ATOMIC RADIO. - The atomic radius is the average distance between the outer electrons and the nucle

JW Doberiner In 1817, German chemist, recommended classification of triad elements since found that the atomic mass of strontium, is very close to the average of the atomic masses similar two metals: calcium and barium.
Found other triads as lithium, sodium and potassium, or chlorine, bromine marble table base and iodine, but as unable to find sufficient triads for the system to be useful.
The successful distribution of the elements was developed by Dimitrii marble table base Mendeleev (1834-1907), Russian marble table base chemist. In Mendeleev's table were prepared mainly elements by increasing atomic weight, although marble table base there were some cases in which he had to place element with atomic mass in a little more before an element with a mass slightly less. For instance, placed tellurium (atomic mass 127.8) before the iodine (126.9 atomic mass) because the sulfur resembled tellurium and selenium in their properties, while iodine was similar to chlorine and bromine. Mendeleev marble table base left gaps in his table, but he saw these spaces as an error, marble table base but would be filled by elements not yet discovered, and even predicted the properties of some of them.
After the discovery of the proton, Henry GJ Moseley (1888-1915), British physicist, determined nuclear charge of atoms and concluded that the items were ordered according to their increasing atomic numbers, so those with similar chemical properties located at regular intervals defined, that we derive the current periodic marble table base law:
GROUPS. - These are vertical columns or rows of the periodic table. The periodic table consists of 18 groups. These are designated with the progressive number, but is widespread designate them as groups A and B groups numbered with Roman numerals
FAMILIES. - They consist marble table base of the representative elements (groups "A") and are:
Halogen
Li
5
F
Family
Valence electrons
: Cu
Pd
The largest coefficient indicates the level which in this case is 5, the last letter indicates the block "d" and in that line on the block "d" has the superscript 7, starting where it initiates the block "d".
8
2
3d
ELECTRONEGATIVITY. - A measure of the pull exerted by an atom of a molecule on the bonding electrons. marble table base In the periodic table in periods electronegativity increases rightward and groups increases upward.
AFFINITY ELECTRONIC. - The amount of energy marble table base released when an atom gains an extra electron. It is the tendency of atoms to gain electrons. Electron affinity periods increases to the right, and upwards groups.
IONIZATION ENERGY. - The amount of energy required to remove the most loosely bound electron to the atom. The ionization energy in periods marble table base increases to the right and in the groups, increases upward.
ATOMIC RADIO. - The atomic radius is the average distance between the outer electrons and the nucleus. Broadly, the atomic radius increases to the left in the periods, and down in groups. Below are the atomic radii of the representative elements expressed marble table base in picometers.
METALLIC CHARACTER. marble table base - The division between metals and nonmetals is clear in the table. Metallic character referred to is marked as metallic marble table base or nonmetallic properties with respect to other elements. Metálicoaumenta marble table base character in periods leftward and downward groups.
Electron affinity decreasing Ra, Fe, N, Cu, W: Decreasing mean high to low, if electron affinity, the largest are the top right, then ordered down and to the left, using the symbol> (greater that).
Increasing electronegativity marble table base Zn, Rb, O, Cr, Al Growing means from lowest to highest, if electronegativity, the least electronegative are bottom left. They are ordered from bottom to top, from left to right and using the <(less than.)
Ionization energy decreasing Zr, Co, C, Sr, Nb
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2013 (20) October (2) PERIODIC CLASSIFICATION OF ELEMENTS marble table base PRACTICE NO. 2 TURBIDITY MYSTERIOUS September (1) August (1) June (2) May (4) April (6) March (1) February (3) 2012 (8) November (1) October (7)