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Bonds weak dative bond

The link is a special form of dative covalent bond. Called dative because a substance is called the employer and other acceptor. It is formed when an element contains one or more doublets available and is typical of non-metals. The most common case is when a species that has an electronic doublet is not shared, such as ammonia, binds a proton H + thus giving rise to the ammonium ion.

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The molecular dipoles can give rise to intermolecular forces of attraction.
intermolecular bonds are dominated by the mutual attraction between dipoles static - it is the case of polar molecules - or between dipoles and ions - is the case, for example, a salt that dissolves in water.
In the case of noble gases or compounds formed by nonpolar molecules can liquefy is explained by the random formation of a temporary dipole when the electrons in their orbits, they are randomly concentrated on one side of the molecule, the dipole induced in the molecules near him is an imbalance of electric charge (the so-called induced dipole) that generates mutual attraction and causes condensation of the gas. The link is then produced by these particular forces of attraction called dispersion forces or Van der Waals forces.
A special case of intermolecular bonding, which can also be when the intramolecular geometry of the molecule allows it, is the hydrogen bond. An atom
hydrogen bound to an oxygen atom (or fluorine), because of its positive polarization and its compact size, relatively high intensity attracts the atoms of oxygen (and fluorine and to a lesser extent, nitrogen) close .
That link, although weak, is responsible for the spatial conformation of proteins and nucleic acids, conformation to which the biological activity of the compounds themselves.

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The ionic bond is a bond between ions of opposite sign. These ions are formed by atoms having electronegativity difference greater than the conventional 1.9: In these conditions, when two atoms approach (a metal and an atom of an element of the last groups), the electrons in the outermost level of the atom less electronegative spend more electronegative atom. This then becomes a negative ion, while the other atom becomes an ion positivo.Questo binding is purely electrostatic, the arrangement of atoms in space is not the directionality of the covalent bond: the electric field generated by each ion is spreads symmetrically in the space around it.

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Ionic bond coordination and covalent bonds delocalized

bond coordination (or dative)
is a special kind of covalent bond that in the past dative because the two electrons involved in the bond come from one of the two atoms that employer (or agent nucleophile), while the other is called acceptor (electrophile or agent) and have an empty orbital in which to "accommodate" this pair.

bonds and delocalized metallic bond
Some covalent bonds, those relocated, they can tie together three or more atoms simultaneously.
The most extreme form of relocation of the covalent bond occurs in the metallic bond. According to this model a metal can be represented as a lattice of positive ions held together by an electron cloud shared across the whole network, since these electrons are not linked to any particular atom, are be highly mobile, this mobility is responsible for high electrical conductivity of metals.

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pure covalent bond A covalent bond is called "pure" when it is formed between atoms with the same value of electronegativity, or between 0 and 0.3. In this case, the electrons are held in common between the two atoms are drawn with the same force on both nuclei and, therefore, are to be shared equally between the two atoms (there is a symmetrical distribution of electron cloud ). The covalent bonds that form between two atoms share two pairs of electrons are called double bond.

Legame covalente polare
Un legame covalente polare si forma tra atomi che hanno elettronegatività diversa, ma non tanto diversa da rendere possibile la formazione di un legame ionico (la differenza dei valori di elettronegatività è sempre minore di 1,7).
In questo caso, i due atomi mettono in comune i loro elettroni spaiati, tramite la sovrapposizione degli orbitali in cui si trovano questi elettroni i quali saranno maggiormente attratti dall’atomo più elettronegativo. Il legame risulterà quindi polarizzato elettricamente, cioè ognuno degli atomi coinvolti nel legame presenterà una carica elettrica parziale, o negativa o positiva.

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Si ha un legame chimico when an electrostatic force holds together more atoms in a molecule or a crystal (strong bonds or intramolecular) or more molecules in a substance in condensed (weak bonds, or intermolecular). The atoms form chemical bonds to achieve a more stable electronic configuration, general electronic configuration of the nearest noble gas, then the octet. The noble gases, which have already reached the octet, do not form chemical bonds.
ties can be strong (pure covalent, polar covalent, ionic, relocation and coordination) or weak (secondary chemical bonds).

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Energy Chemical bonds Chemical bonds

To remove an electron in an atom, and then it becomes an ion's can provide a certain amount of energy is called ionization energy which is the minimum energy required to remove it from \\ to an electron and bring it to an infinite distance and which is measured in kilojoules per mole (kJ / mol) in kilocalories per mole (kcal / mol) or electron volts (eV). It depends on the atomic species. Naturally, the more the electrons are close to the nucleus (as in non-metals), the greater the amount of energy that must be given to remove the electrons from the atom. If
leaves the first outer electron from the atom, energy is called the first ionization energy. This posts a p electron, the second one detaches from the s sublayer full s. The third ionization energy of the electron is greater because, while the atom loses electrons, its nuclear charge is constant and the remaining electrons are held more firmly.
The fourth ionization energy is about four times the third.

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The chemical bond is a force of electrical attraction that holds together atoms in molecules and crystals.
There are different types of bond but in any case, the forces holding the atoms are always due to electrical attraction between oppositely charged particles. When two atoms bond, the resulting molecule is a system to lower energy and therefore more stable than the two isolated atoms, this is why there are very few in natuira isolated atoms. There is a difference of energy that exists between the isolated atoms and those legatui and represents both the energy released in bond formation is the energy that we must provide to break free and regain the atoms. The binding energy is energy that must provide a bond to break and this amount is equal to that which is released when that bond is formed.

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ionization ionization, the danger of ionizing radiation and the ionic bond

ionization
The phenomenon of ionization is the separation of one or more electrons from atoms or molecules to which they belong, who are charged accordingly positively. Ionization does not result in generation of net electrical charge, but a provision of electric charges for subsequent recombination and reactions within the irradiated field. In physics, fully ionized atomic nuclei, such as alpha particles, charged particles are commonly known. Ionization is usually performed by applying high energy to the atoms in the form of electric potential or radiation. An ionized gas is called plasma. The negatively charged ions are known as anions (which are attracted to the anode) and the positively charged are called cations (and are attracted to the cathode). Ions can be monovalent (indicated by a + or -), divalent (with two + or -) and trivalent (three +). Then ions are divided into monoatomic and polyatomic. For single atoms in a vacuum, there is a physical constant associated with the ionization process. The energy required to remove electrons from an atom is called ionization energy or ionization potential.

The danger of ionizing radiation
Ionizing radiation produces damage: a consequence of the ionization produced by radiation are generated within the new cells, molecules or fragments of molecules very aggressive from the biochemical point of view, capable of irreparably damage at the molecular structures responsible for cell function, or integrity the genetic heritage. The damage can be immediate if radiation dose is likely to directly inhibit the functions of the cell body or bodies to which they belong, or delayed in time in case of damage to the genes of the cell. The amount of radiation energy needed to produce damage, even very serious, is, in absolute terms, very small: nothing compared to the energies involved in the most common tasks of daily life, such as heating a saucepan of water , ol 'pile driving a nail to the wall. For example, the energy of a beam of ionizing radiation can induce, if consumption of the whole body, the death of the irradiated within thirty days with a probability of 50% (an effect therefore of the utmost gravity) would, if fully converted into heat energy, raising the temperature of the body of a thousandth of a degree centigrade, quite negligible. In comparison, the threshold for the onset of physiological effects due to heating by non-ionizing radiation (radio waves, microwaves, ...) is 1 ° C rise in body temperature or by irradiation of the party concerned. Therefore, the risk of ionizing radiation is not due to their high energy content in absolute terms, but the extreme effectiveness of their destructive action against the molecular structure of organized living matter.

The
The ionic bond ionic bond is a type of bond that can take place only between different atoms.
We know that many atoms can be ions, for purchase or loss of electrons: some
, which have low ionization energy, they can easily give cations losing a certain number of electrons, thereby taking an equal number of positive charges. Other
, with high electron affinity, can make a number of anions by accepting electrons, thereby taking an equal number of negative charges. Anions and cations are attracted by electrostatic interaction: this interaction is called ionic bonding. All atoms of 1, 2 and 3 group create ionic bonds with the exception of hydrogen (H) that will create the covalent bond (a bond formed by a pair of electrons shared between two atoms), then the elements of the 5th, 6th and 7th group will buy 3 respectively, 2.1 electrons, these atoms gain electrons because they are very electronegative and tend to attract to that if the electrons, while the 1st, 2nd and 3rd group to become stable electron must give respectively 1,2,3.
ionic compounds are characterized by high melting points and ability to conduct electricity in molten state and in aqueous solution, tend to be soluble in water and crystallize.

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The first ionization energy of an element is the energy that must be used to remove the outermost electron from an atom in a gaseous state. The energy of the second, third and so on .... ionization energy is used to remove the second, third, etc. .... electron.
The ionization energy is measured in kJ / mol.

is meant to indicate that the energy required to tear an electron to an Avogadro number, 6.022 x 10 23 atoms of that element.



The ionization energy is greater than the electron is more strongly linked to the nucleus and this is natural because to win a high force is necessary to use more energy.

Remember that electrons, negatively charged particles are attracted to the nucleus where it is concentrated all the positive charge and are more attracted to the higher is the number of protons, that is, the greater the positive charge of the nucleus and the more they are close to the nucleus.

So if we imagine an atom to pull all its electrons starting from the outer gradually until the last that remains, it is easy to imagine that the ionization energies increase as you get closer to the nucleus because the electrons will be retained this with ever greater force.

The second ionisation energy is greater than first-ionization.
The second ionization energy is the energy required to tear an electron to an atom, or rather an ion, which had been previously torn.

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Alkali

series of six chemical elements of group IA (1 in the IUPAC nomenclature) of the periodic table. Are tender when compared to other metals and melt at relatively low temperatures. From the chemical point of view, the alkali metals are strong reducing agents: In order to achieve a stable electronic configuration, for they give in easily the single outer electron belonging to the orbit; react violently with water to form metal hydroxides and releasing hydrogen , which caught fire in the air high reaction temperature. Their high reactivity makes them difficult to find pure nature.

In order of increasing atomic number, they are: lithium, sodium, potassium, rubidium, cesium and francium. This element exists only in radioactive form.

Lithium is the founder of the family of alkali metals. It 's the first solid element, since it follows the hydrogen and helium. It 's a very light metal, because its density is about half that of water. And 'the element with the standard reduction potential more negative. These characteristics are, not surprisingly, the key component of the latest battery technology for electronic devices. In the picture you see it float on the solvent in which it is stored.

Sodium is an element to all known and heard, mainly on mineral water. It too is an alkaline and not many know that apart when dissolved in water, is a soft, silvery, easily cut with a knife. Because of its high reactivity is preserved in oil or Vaseline petroleum ether.

Potassium, also tender and brightly colored metal, is characterized by sodium and lithium ahead of him for even greater responsiveness.

rubidium, retain the same properties as its cousins \u200b\u200balkaline but is distinguished by a very high price, of nearly € 150 per gram!

cesium, which is also very expensive, although not as rubidium, has literally marked our time: In 1967 the Thirteenth General Conference on Weights and Measures defined the second as the duration of 9,192,631,770 periods of radiation corresponding the transition between two hyperfine levels of the ground state of the cesuio 133.

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elements of internal transition - Lanthanides and actinides

ELEMENTS OF INTERNAL TRANSITION -
lanthanide elements and actinide elements of the block f are commonly called inner transition elements or rare earths
what you thought were not very common in nature. They consist
Two series of 14 elements and are arranged in the 6th and 7th period between the 3rd and 4th
group of the periodic table. Usually they are represented separately from other items
simply for a more meaningful representation of the periodic table itself.
The two series are also indicated by the name of the element that precedes each of them. So we will have the series of lanthanide or lanthanides (6th season) and actinides or attinoidi (7 th period). The Lanthanides

character elements are metallic, silvery-white, highly electropositive and reactive
. The atomic radii are very similar (between 1.02 and 0.86 Å). Their chemistry is so similar as to have led, until 1907, to consider a single element.
The lanthanides are all in nature, with the exception of promethium (Pm, Z = 61 and obtained synthetic), which are only found in compounds. Although it is commonly known as rare earths and nature have a certain abundance. For example, the Ce (6.6 ° 10.3% by weight in the crust; 25 th most abundant element) has an abundance similar to that of Cu and is about four times more abundant than Pb.
Actinide

character elements are metallic, silvery-white, responsive.
are all radioactive, with short relatively short half-life (except for 232Th, 235U and 238U have t ½ comparable age of the earth and are called primary source).
The only elements of the actinide series to exist in nature, even if not widespread, are Th, Pa and U.
All others have been produced synthetically by nuclear reactions.

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metals, non - metals and metalloids ..... The chemistry of carbon

elements belonging to groups 3, 4 and 5 A include both metals and non - metals.
The metallic character of the elements increases as you go down the table and the last member of each group shows metallic properties.
The classification of elements as metals or non - metal case based on their electronic structure and are
- M Etalle : Elements with a number of outer electrons low, less than or equal to that of the external orbital sep, and with low ionization energy. Therefore, the transition elements, the lanthanides and attinoidi have 1 or 2 electrons if the metallic character increases going down each group;
- N on-metal : elements with numbers greater than the number of electrons outside the outer orbitals sepe with high ionization energy.
- In addition there are the metalloids : elements that can behave like metals or non-metals in particular situations, are those of the border between the two types.

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The elements contained in Group 5 of the periodic table (prepared according to IUPAC ) are:
vanadium (23)
niobium (41)
tantalum (73)
dubnium (105)
These elements are classed in Group 5 because their 5 electrons in the valence shell. Dubnium not exist in nature.


Vanadium Vanadium is the ' chemical element of atomic number 23. Its symbol is V. It is a rare element, soft and ductile, which is in the form of a compound in certain minerals. It is mainly used in metallurgy for the production of alloys.
Features: V is present in abundance of 0.0136% (136ppm) that is the 5th most abundant element among the later transition elements Fe, Ti, Mn and Zr
Vanadium is a bright white metal, soft and ductile. It has good resistance to corrosion by alkali , 's sulfuric acid and ' s hydrochloric acid. Exposed to ' air you oxidizes rapidly at temperatures above 933 K (660 ° C).
Vanadium has a good consistency and a small cross section with neutrons from nuclear fission , making it suitable for use in applications related to nuclear energy production . Chemically
shows an intermediate response between metal and non-metal both acid that basic . The
oxidation states most frequently assumed by the vanadium compounds are +2, +3, +4 and +5. In a laboratory experiment can be observed colorimetrically by the passage of these vanadium oxidation states during the reduction of ammonium vanadate with NH4VO3 zinc metal.
In rare cases, the vanadium oxidation may also take the number of +1.


Niobium Niobium, also formerly known by the name of Columbia because the discovered together tantalum in the mineral columbite , is the ' chemical element of atomic number 41. Its symbol is Nb. It is a transition metal rare, soft, ductile, gray. Is extracted from niobate and is mainly used in the production of special alloys and high strength welds.
Features: Niobium is a shiny gray ductile metal that takes on a bluish tinge when left exposed to air at room temperature for prolonged periods. The chemical properties of niobium are similar to those of tantalum, which belongs to the same group of the periodic table of the elements, this similarity in the reactivity of Nb and Ta is due to the fact that their dimensions are almost identical, strange thing can be explained by the lanthanide contraction .
Even at high temperatures, is processed in an inert atmosphere, since already at 200 ° C tends to undergo oxidation . His
oxidation states most common are +2, +3 and +5.


Tantalum Tantalum is the ' chemical element of atomic number 73. Its symbol is Ta.
is a transition metal hard and malleable, shiny, blue-gray, very resistant to corrosion, especially the attack of acids , and is a good conductor of heat and electricity. It is rather rare in nature and is found in mineral tantalite . Tantalum is used in surgical instruments and installations intracorporeal implants, because they do not react with body fluids.
Features: As already stated, tantalum is highly resistant to corrosion, in practice, at temperatures below 150 ° C , it can be considered completely immune to chemical attack, even at extremely aggressive substances as the ' aqua regia, and can be affected only by' hydrofluoric acid, from acid solutions containing fluoride ion and sulfur trioxide free. Tantalum has a very high melting point, surpassed only by tungsten and rhenium (3290 K melting point, boiling point 5731 K). Tantalum has the highest electrical capacity specific than any other substance.

Dubnium
Dubnium 's chemical element in the periodic table of elements, that has the symbol Db and atomic number as 105.
is a synthetic element, highly radioactive isotope which has a more stable half-life of less than 40 seconds. This element therefore has no practical applications and its properties are poorly understood.

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Carbon is a special element, can form carbon composti.Il million in the second period and belongs to group 4. Has Z = 6, denoted by the symbol C, atomic weight 12.01115. The most abundant naturally occurring isotope is 12C, 13C are also eil 14C.La electronic configuration of carbon is 4, tells us that epiùesterni, disponibili.Il C can then form 4 single bonds.

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Link fifth group on the periodic table

http://corsiadistanza.polito.it/corsi/pdf/9065N/modulo/chimica5.pdf

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THE ATOMIC ORBIATLI

Please display an atomic orbital, it is approximated with that part space around the atomic nucleus where the probability of finding an electron is maximum. This means that a region of space around an atomic nucleus is used to graph an orbital orbital can atomico.Questo be represented by a cloud with a density of color is directly covered proportional to the probability of finding an electron at that point. To calculate the probability that an electron is in a given space is multiplied by the square of the wave function for the volume dr.
The number and the extension of atomic orbitals can be obtained from the solution of the Schrodinger equation.
For the Pauli principle, each electron can cntenere than electrons. Rempe starting orbitals are those with minimum energy and gradually filling those supeiore of energy.
If there are any orbital degenerate orbitals are distributed preferezialmente to fill as many

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First group - Alkali metals Group











The first group of the periodic table is divided into two groups: Group 1 A

includes elements with a single monovalent outer electron nell'orbitale type s.

Except for hydrogen (with special characteristics), the elements that compose it are alkali metals.

latter react violently with water, and develops considerable heat:
- Hydrogen (H Symbol, Z = 1) is the lightest and most abundant element in the universe, incolore, inodore ed è altamente infiammabile;
- Il litio (Simbolo Li, Z=3) è un metallo soffice di colore argenteo, altamente ossidabile;
- Il sodio (Simbolo Na, Z=11) è, come il litio, un metallo soffice e argenteo, ma è molto reattivo e brucia facilmente;
- Il potassio (Simbolo K, Z=19) è un metallo soffice bianco-argenteo, dalle caratteristiche chimiche simili al sodio;
- Il rubidio (Simbolo Rb, Z=37) , di colore bianco-argenteo, è debolmente radioattivo e spontaneamente infiammabile all’aria;
- Il cesio (Simbolo Cs, Z=55) è un metallo alcalino di colore argenteo-dorato, tenero e duttile, ed è uno dei tre metalli che si possono found in the liquid state at room temperature;
- Francium (Fr Symbol, Z = 87) is the heaviest of the alkali metals and unstable, and is the natural state in uranium and thorium.
Group 1 B includes in copper, silver and gold, which can have value greater than 1.
are called "transition metals" because they must be regarded as terms of the following passage from Group 8 Group 1:
- The copper (symbol Cu, Z = 29), reddish in color, has a high electrical and thermal conductivity, ductile, malleable, and is also highly resistant to corrosion;
- The silver (symbol Ag, Z = 47), white and gloss is the best conductor of heat and electricity between metals, occurs naturally in mineral form and pure;

- gold (symbol Au, Z = 79) is a transition metal soft, heavy, ductile, malleable and yellow. And 'only attack directed water and mercury, and is a state of nature in the form of flakes or nuggets.

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According to the orbital elements of the model should be a group are characterized by an electronic configuration with five electrons in the valence shell, which is why in previous conventions this group was called before VA, then 5A.
Nitrogen and phosphorus are not metals, arsenic, with very similar properties to phosphorus, is a metalloid, antimony and bismuth metals. The most common oxidation numbers for this group are ± 3, ± 5; exception is nitrogen, which also offers ± 1, ± 2, ± 4.

Nitrogen is a chemical element with atomic number 7. Its symbol is N (from the Latin Nitrogenum). Nitrogen is the main component of the organic molecules important in terms of biochemical (DNA, proteins, vitamins), as well as extremely popular and important inorganic compounds such as ammonia and nitric acid. The molecular nitrogen (N2, consisting of two nitrogen atoms) is a colorless, odorless, tasteless and inert, which accounts for 78% of Earth's atmosphere (this is the most common gas in the air). Nitrogen is the fifth most abundant element in the universe, the 19th Earth's crust, which is 0.03% and the fourth in the human body, which is 3%.
Phosphorus is a chemical element with atomic number 15 and symbol P.È a non-metal group nitrogen. Phosphorus is not found in nature at its most elementary, but in the form of phosphate (salt of phosphoric acid), is abundant in rocks and in living cells, whose metabolism is an essential component. The main industrial use of phosphorus in fertilizer production. It is also used in the production of explosives, matches, fireworks, pesticides, toothpaste and detergents. Phosphorus appears as a white waxy solid with a characteristic unpleasant garlic odor, and when is very pure and transparent. It is insoluble in water and soluble in organic solvents, such as carbon disulfide. Upon contact with air burns spontaneously forming phosphorus pentoxide, P2O5.
Arsenic is a chemical element with atomic number 33. Its symbol is eg rotary is a semi-metal that comes in three different allotropic forms: yellow, black and gray. Pure arsenic is not poisonous, but they are all compounds that are used as pesticides, herbicides and insecticides.
antimony and a chemical element with atomic number 51. Has the symbol Sb, from the Latin meaning stibium stick. It is a semi-metal that comes in four different allotropes. The stable form has a metallic bluish-white, unstable forms have yellow or black. It is used as an agent and flame retardant to produce paints, enamels, ceramics and rubber, and a wide range of metal alloys. As a semi-metal, antimony has the look of a metal, but does not have the typical physical and chemical behavior. In its elemental form is a white solid bluish-silver hues that have low electrical and thermal conductivity and that sublimates at relatively low temperatures. Reacts with oxidizing acids and halogens. Antimony and its alloys expand on cooling.
Bismuth is a chemical element with atomic number 83. Its symbol is Bi. It is a heavy metal and fragile-looking white-rose whose chemical behavior is similar to that of arsenic and antimony. It is the most diamagnetic of metals and, with the exception of mercury, the one with the lowest thermal conductivity. It is a brittle metal with a white color with pink and iridescent. It is the heaviest of the so-called "heavy metals" and is the only one of them not to be toxic. It is the metal that has the highest resistivity.
On heating in air may ignite and burn with blue flame, producing fumes yellow oxide of bismuth.

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Fifth Group two - alkaline earth metals Group

the second group, called the alkaline earth metals, are part of Beryllium, magnesium, calcium, strontium and barium. These elements have two valence electrons in divalent as hydrides are obtained as BeH2, MgH2, and oxides such as MgO, CaO, ... They are all soft metals, malleable, very light and good conductors of heat,
with very different properties and reactivity . Beryllium is very hard, has a relatively high melting point, and gives rise to highly toxic compounds. Even the metal, reduced to dust, it is toxic. It 'also the least reactive of the group. Magnesium is known to all, and is the industrial metal lighter. Football, as everyone knows, is a component of bones and is present in the plaster, as well as a myriad of other compounds. Elementary state is very reactive, as it is preserved under liquid paraffin. Strontium and barium are heavier than the previous ones, are also more responsive and less known. They react readily with water creating hydrogen.

Other material on the reactivity elements of the second group: http://www.tavolaperiodica.it/reattivita_metalli_alcalino_terrosi.html

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The elements of group VI are: oxygen, sulfur, selenium, tellurium and polonium. The oxygen and sulfur are nonmetals, the metalloids selenium and tellurium are semiconductors, while polonium is a metal. The main features are:

• all are solid at room temperature, except the oxygen and gaseous
• their atoms have six outer electrons, two on a type s orbital, and four out of orbit type p;
• have all the oxidation state of -2 when they bind to the less electronegative. When they bind to electronegative elements are the oxidation states +4 and +6, with the exception of oxygen, this being the second element after elttronegatività fluoride, has a positive oxidation state only when bound to fluorine (and in this case states can take +1 or +2);
• have two pairs of paired electrons, and thus can form two dative bonds with the role of donors; exception of oxygen, which, given its high electronegativity, it does not behave donor, acceptor, but, as an acceptor and can form a single dative bond;
• hydrogen forming compounds which are present in an atom and two hydrogen atoms of the element.

The elements of Group VI A, the group also Ext 16, are called chalcogens, the name has generally been derived from the Greek words chalcos "mineral" and-gen "formation", then the generator of minerals. The compounds, including sulfides, tellurides and the selenuri are also known as chalcogenides.

Oxygen was discovered in 1774 by Joseph Priestley, was known from ancient sulfur, selenium was discovered in 1818 by Jons Jacob Berzelius, tellurium in 1783 by von Mueller Reichestein, and polonium in 1898 by Pierre and Marie Curie.

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Sixth Seventh group

Group 7 of the periodic table consists of elements :
manganese (25)
technetium (43)
rhenium (75)
Bohrium (107)
these elements are classed in Group 7 because they all have 7 electrons in the valence shell.
Manganese is a metal, is the ' chemical element in the periodic table that has the symbol Mn and atomic number 25. Technetium
's chemical element of atomic number 43. Its symbol is Tc.

Rhenium 's chemical element of atomic number 75. Its symbol is The King

Bohr 's chemical element in the periodic table of elements, that has the symbol Bh and atomic number as the 107.

At room temperature, these elements are all solid, the color red for the atomic numbers indicates that the element is synthetic and not found in nature.

Halogens.

The halogens are a group of highly reactive elements, these tend to acquire an electron to achieve a stable electronic configuration. Fluoride is a colorless, highly reactive gas that is able to attack even the glass. Chlorine is a gas instead of the characteristic yellow-green pools. Bromine is a red volatile liquid scent irritant. Iodine is a dark purple solid that sublimates easily, leaving brown spots in the point where it is placed. These elements are strong oxidants are corrosive and in some cases respond to simple contact with a reducing agent.

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Periodic properties of elements in the periodic table

the early nineteenth century, scientists began to tidy up the increasing amount of information they had available. In 1869, these efforts culminated in the 'development of what today is called the periodic law, which states that certain physical and chemical properties to express themselves at regular intervals when the elements are arranged in order of increasing atomic number.
Frequency In chemistry, Law which states that the chemical and physical properties of the elements recur in a systematic way for atomic numbers increasing. In the periodic table the elements are distributed according to the external electronic configuration. In particular, see the table in vertical position (for groups), we find elements that have the same number of electrons nell'orbitale outside, and for this reason they have similar physical and chemical characteristics. Instead of moving in a horizontal direction, ie by reading the table for periods, we find that electrons in atoms present nell'orbitale outer rise, continuously, from 1 to 8. When a period is completed, it will start a new one, so that the configurations external electronic, and with it the chemical properties of elements change periodically repeating line by line (ie, period by period). Adjacent elements within a period, therefore, have an electronic structure that varies regularly through it and therefore are characterized by a parallel change of ownership. The most important periodic properties: atomic radius, ionization, electron affinity and electronegativity. More precisely, the atomic radius increases moving in the periodic table from top to bottom, ie in individual groups and decreases from left to right, ie in each period. The first ionization energy, the affinity Electronic el'elettronegatività increase from left to right in the periodic table, but decrease from top to bottom.

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CHEMISTRY? Eighth

The tests covered by REACH (Registration, Evaluation, Athorisation of Chemicals) consist, for the majority of cases, chemical testing on animals. In 2005 it was estimated that it would have been killed up to 50 million. It
experiments on rats, rabbits and dogs to determine whether a substance
- is toxic to humans
- is harmful to human eyes
- is irritating to human skin
- causes cancer or birth defects in humans
- interferes with the human endocrine system (glands, liver, pancreas, etc.)

But significant differences in anatomical, physiological, biochemical and metabolic between organisms of the species on which human experiences and the body, are such as to make reliable and truthful human application of the results animals.
Here are some of the most glaring example.

IRRITATION
How : an animal commonly used, and provided for in the REACH for eye irritation is the albino rabbit. In most cases it is not expected anesthesia. With this experiment we try to identify the irritation caused by a substance that comes in contact with eyes. Is introduced in one eye (the other serves as a control) a predefined quantity of the substance to be tested, and we study the possible reactions: flushing, redness, swollen eyelids, ulceration, lacrimation.

Critique: The ocular responses to a chemical substance is closely related to the anatomy of the eye and the immune status, physiological and genetic animal. And also: •
the human eye is structured very differently than in the albino rabbit. •
our cornea is thicker and covers a lower percentage of ocular surface. •
an ocular membrane (M Bowman's) man is six times thicker. •
our tears is able to expel harmful substances while the rabbit is very low and the substance remains in the eye for longer
• eyelids, which play an important role in the removal of substances, are very different .
The degree of irritation is also evaluated in a totally subjective operator running the test, so the response will depend on its experience and sensitivity and not by objective evidence.

Alternatives: You can alternatively take an integrated study based on mathematical methods, statistical and chemical, for example by simply measuring the pH of the substance. Or make use of other biochemical tests such as measurement of proteins released by the tear fluid after exposure to the substance.

TOXICITY 'REPEATED
How : the repeated dose toxicity testing required by REACH involves the use of 60 rats for each substance and possibly 32 dogs. The experiment aims to identify the toxic effects on humans following the administration of repeated doses of a chemical. The substance analyzed is introduced repeatedly in the animal - usually by force-feeding - for a period 28 to 90 giorni.Durante
the experiment can be observed: •
pressure changes
• anemia • aggression


• muscle weakness • tremors •

• coma and sometimes death
At the end of the test period are killed animals remained alive and passes to the analysis of their tissues and internal organs.

Critique: The way a body reacts to chemicals depends on its metabolism. Between man and mouse (or dog) that are normally made these experiments there are significant differences in metabolism
• the speed with which the substances are metabolized varies depending on the size and weight •
enzymes involved in the processes of reaction vary from species to species
These differences mean that the same substance can be expelled in some animals and accumulated in other, resulting in entirely different effects.

Alternatives: You can use an integrated mathematical and statistical methods and in vitro tests. The first permit to study in detail the chemical and physical characteristics of the molecule and provide a prediction of possible effects. The results can then be confirmed through in vitro studies.

CARCINOGENESIS
Procedure: The test carcinogenesis is provided by the REACH with the use of at least 400 rats for each substance to be tested. Immediately after weaning is administered to young rats the chemical and then evaluate the outcome of exposure through blood, tissues and organs. The test lasts 5 years. All animals involved die of diseases induced during the trial or were killed for carrying out the analysis.

Critique: between the human organism and animals commonly used in testing for carcinogenicity, there are a number of differences that can not be considered for man results. For example: • the speed with which
a substance is metabolized is usually inversely proportional to the size of the animal (in mice and rats, so this process is much faster than humans).
• mice and rats in the B cell growth is very fast (they unamaggiore predisposition to and development of cancer). •
bodies of rats, mice, dogs, cats and hamsters are able to self-produce vitamin C, one of the most important antioxidants and protectors against cancer, while the man needs to take it with food.
Alternatives : testing for carcinogenicity, since the 70's are used in vitro methods that use to bacteria. These tests which have proved crucial in the fight against cancer. For example, thanks to in vitro methods: •
has discovered the mechanism that turns healthy cells into cancer cells
• have identified the characteristics that determine tumor cell proliferation and thus tumor growth.

Nothing really cruelty free because all the substances have been tested on animals in the past as today, what we can do but 'is not buying products with ingredients of the new generation and therefore must be tested for not increasing the vivisection .

Here are the sites for useful information and list no cruelty brands of personal products not tested on animals:)

http://www.lav.it/
http://www.lavocedeiconigli.it/lista_% 20nocruelty.htm

Gravestone Quote Father

group - Noble gases and their compounds

The term noble gases comes from the fact that, to paraphrase the attitude of the nobility, avoid these gases react with the elements common. The noble gases were also called inert gases, but the term was not accurate, because some of them have been shown to take part in chemical reactions. The noble gases do not react with the regular items, do not match, or rather, Silver Haze, but not evenly, like when you put the oil in the water, if known, while stirring vigorously for minutes and minutes you can not mix it evenly. A mixture of noble gases is a chemical compound that contains elements in Group 18 of the periodic table. The hydrates are formed by compressing the noble gases in water. The heavier atoms form more easily its derivatives, Xe 6H2O hydrate is more stable. The clathrates
are composed of noble gases which are trapped in the cavities of the crystals of some organic substances and not. To make sure that you create the atom and the host must be large enough to be fixed in the cavities of the crystals.
The clathrates are used to separate helium and neon from argon, krypton and xenon. Compounds that contain unstable nuclides of noble gases keep their properties clear of decay: the clathrate of 85Kr, for example, emits beta particles, while the clathrate emits gamma rays of 133Xe.
particles beta: The beta radiation is a form of ionizing radiation emitted by certain radioactive nuclei such as cobalt-60;
gamma rays: a form of electromagnetic radiation produced by radioactivity or other nuclear or subatomic processes . Gamma rays are more penetrating than either alpha or beta radiation, but are less ionizing

How To Build A Big Green Egg Table

The political philosophy of Karl Popper 2

The critique of Comte and John Stuart Mill
of Renzo Grassano

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trend is not a law - says Popper.
"A proposition affirming the existence of a trend is existential, not universal."
As already demonstrated, "a universal law, not state the existence of something ... but asserts the impossibility of something ..."
The logic of this distinction has important consequences decisive.
According to Popper, in fact, we found estimates of social value on scientific laws, but not about trends.
"The distinction famous since the time of Comte and Mill between laws of coexistence, which would match the static and the laws of succession corresponding to the dynamics, it can - we agree - be interpreted in a a reasonable manner, that is, it may be a distinction between laws in the wording of which is the time participant (for example laws that speak of speed), and laws that have no reference to the concept of time. But it is precisely what they had in mind Comte and his followers. Saying the laws of succession, Comte thought to the laws that determine the inheritance of a dynamic series of phenomena, the order in which we observe them. Now it is important to realize that the laws "dynamics" of succession, such as Comte thought, absolutely no ... [...] What is the closest to them, and who probably thought, are recurring phenomena, like the seasons, phases of the moon, eclipses or maybe the oscillations of the pendulum. But these intervals, which in physics could be described as dynamic (albeit stationary), would, in the sense of the committee set term, "static" rather than "dynamic" in any case could hardly be described as "laws" (as they depend on special conditions prevailing in the solar system ...) I will call "quasi-law of succession." '(1)

the Austrian philosopher says: "... yes we can assume that any sequence of real phenomena proceeds according to the laws of nature, but it is important that we realize that no sequence of, say, three or four related phenomena proceeds according to one randomly law of nature. When the wind shakes a tree and drop to the ground Newton's apple, no one denies that these events may be described in terms of causal laws. But there is one law, like gravity, or a single well-defined group of laws that can describe the actual sequence of events as a succession of causally related events: in addition to gravity, we should consider the laws that explain the pressure wind, shots of the branch, the tension in the stem of the apple, the apple products in bruises from the collision, the subsequent chemical processes, etc.. The idea that any specific series or sequence of events (apart from the movements of the pendulum, or the solar system, or similar examples,) may be described or explained by a single law, or a group of well-defined laws, is simply wrong. There are no laws of succession, nor laws of evolution.
Yet according to the concept of Comte and Mill, their laws of succession would lead to a series of historical events in the order in which they were actually presented, we can infer from the way in which Mill speaks of a method that "is groped to find out, through the study and analysis of the general facts of history ... the law of progress which the legislation once it was, should ... give us the ability to predict future events, at the same so that, in algebra, after only a few terms of an infinite series, we can see the principle of regularity of their formation, and predict the rest of the series up to any number of terms. This method to maintain a critical attitude, but his critics (see the principle in paragraph 28) widely acknowledges the possibility of finding laws of succession similar to those of mathematical series, although expressing doubt that "the order of succession ... that history shows us "not so" strict standard "to be compared with a mathematical series." (1)

Once recognized, however, in Comte and Mill some merit in the field of epistemology, particularly the critical to 'essentialism (2), Popper believed to give a close almost final lesson, explaining that the method is fundamental.
When you collect data (evidence, facts, set of facts in this case, historical events, ed) to some conclusions about their meaning, not just start with the observations, as some scholars. "... is necessary for the emergence of an interest with respect to our data of a certain story: first of all, it always presents the problem . The problem in turn can be suggested by practical needs, or scientific or pre-scientific belief that for whatever reason seem to need revision. "(1)

In a long and rigorous examination of Mill's thought about the explanation , understanding causal explanation, Popper received a first conclusion: in his thoughts, and to Mill "there is not much difference with regard to the reduction of laws to other more general laws, ie the causal explanation of regularities ".
But Mill is on a "use is not clear" because the term . It is used both to denote the universal laws, is to highlight unusual events.
This creates confusion and leads Mill to a blunder: to ignore, namely, that the persistence of trends is closely related to the initial conditions that have made the same trend. "Mill and his fellow historians have not noticed the trend of the dependence initial conditions. Ensure laws as if they were absolute laws. The confusion between laws and trends that are causes they believe in unconditional trends (and general), or shall we say, trends in absolute, for example, in a general historical trend towards progress - "a trend toward a better state and happier ...
[...] Here, we can say, the central mistake of historicism. His "law of development" turn out to be absolute trends, trends such as laws, which do not depend on initial conditions, and that irresistibly draws us into a certain direction in the future. "(1) Continuing

, Popper devotes ample space to compare between the methods of physical sciences and social scientists, ending up talking about his own conception of epistemology. In particular, stresses the importance of experimental trials. But there is one important step that deserves mention because it highlights the stringency used in the logical reconstruction of the birth of a theory: "Import ... realize that in science we must always deal with explanations, predictions, experiments, and that the method we use to test the hypothesis is the principal part [...] invariable: the hypothesis under consideration - for example a universal law - together with some purpose other propositions are accepted without discussion - for example the initial conditions - we infer prognosis. This prognosis then compare, whenever possible, with the result of other experimental observations. If the prognosis and the observations agree, the hypothesis is considered validated, though not confirmed at all, if they are clearly divided, the hypothesis is considered disproved, and his false evidence.
According to this analysis there is not much difference between the explanation, prediction and experimentation. This is not a difference of logical structure, but in emphasis, it depends on what we consider problematic. If we consider the prognosis is not problematic, and instead issues the initial conditions or some of the universal laws (or both) from which we can deduce a date "prognosis" and we say that this is an explanation (And then the prognosis becomes explicandum). If we consider non-issues laws and initial conditions and we serve only to deduce the prognosis in order to obtain new knowledge, we say that it is a prediction . (This is the case in which we apply our scientific results.) And if we consider a problem of the premises, that is, or a universal law or an initial condition, and whether the prognosis can be determined by experience, then we say that he subjected the premise problematic experimental evidence . '(1)

And here we are at the heart of Popper's conception, much like what we saw in the files on von Hajek . After stating that the
as was found theory is a fact of nature completely private (mah?), Popper says that it is rather important question, "How did you feel your theory?". It 's the only question that matters from a scientific perspective. (More mah?)
He explains: "Now, I am convinced that this applies not only to the natural sciences but also social ones. And in the social sciences is even more evident than in the natural we can not see and observe the objects before our thinking to them. In fact, most of the objects of social science, if not all, are abstract, they are theoretical constructions. (For some it will seem strange, but even "war" or "army" are abstract concepts. Dead men, men in uniform, etc.. - That is what is real.)
These objects, these theoretical constructions that we use to interpret our experiences, resulting from the construction of certain models (especially institutions), to explain certain experiences - a theoretical method well known in the natural sciences (in which we construct models of atoms, molecules, solids, liquids, etc..), and which is also part of the method of explanation by way of reducing or deduction of hypotheses. It 's true that very often we do not realize that we are working theories, and that we delude ourselves that our theoretical models are "things", but this is a very common kind of error. This explains the use of models, and at the same time destroys the thesis of essentialism methodology. He explains, because the model is abstract or theoretical, and we believe we can easily see it in the middle of the turn of events observable or behind them, as a kind of permanent or range of essences. It destroys them because the task is to build a social theory and sociological analysis of our models carefully in descriptive terms nominalist, ie in terms of individuals, their attitudes, their hopes, their relationships, etc.. - The assumption that we can call "methodological individualism. (We've seen in von Hajek, ed) '(1)
Not surprisingly, Popper cites von Hajek paragraphs rather than taking long to arrive, however, to affirm unity of method between the natural sciences and social sciences, while acknowledging some differences.
In the next chapter we shall see these aspects of Popper's theory as to the method.
notes:
(1) Karl Raimund Popper - The Poverty of Historicism - Feltrinelli 1975
(2) essentialism is derived from Aristotle's doctrine was the approach each and every problem that exists with the question "What is it? ", provoking a response of the descriptive claim to arrive at a definition expressing the essence of something. For example, for Aristotle, man is two-footed animal, rational, political (in the sense of friendly and cooperative, but also of slavery ... ahem) Popper claims to be "nominal," that is fierce opponent of essentialism. For a nominalist phenomena can only describe, but you can not tell what it is, for example, a man, or what the "light". Nominalism is in fact a consequence of the birth of modern science, from Galileo and Newton.