Explain giving justification the trends in the following properties of elements, on moving , from left to right in a period, in the Modern periodic Table.
(a) Variation of valency. (b) Change of atomic radius .
(c) Metallic to non-metallic character. (d) Electronegative character.
(e) nature of oxides.

Explanation

Properies of elements on moving from left to right in a period.
(a) Valency, ON moving from left to right in a period, the valency of elements increases from 1 to 4 and then decreases to zero. This is because the first element of every period has 1 valence electron and the last element in every period has 8 valence electrons except for the first period.
(b) Atomic radii. On moving from left to right in a period, the size of the atoms decreases. This is because on moving left to right in a period, the atomic number of elements increases. It means the number of protons and electrons in the atoms increase and extra electrons are being added to the same shall. Due to large positive charge on the nucleus, the electrons are pulled in more close to the nucleus and the size of atom decreases.
(C) Metallic to non-metallic character. On moving from left to right in a period, the metallic charater of elements decreases but the non-metallic character increases. Since the size of the atom decreases on moving from left to right , the removal of electrons from the outermost shell becomes difficlt . On the other hand, addition of electrons becomes easy.
(d) Electronegative character. In increases as we move from left to right along the period, As we got from left to right in the periodic table, the reactivity reduces as a result giving away of electrons reduces and taking electrons increases. Henc, electronegativity increases.
(e) Nature of oxides. On moving from left to right in a period , the bais nature of oxides decreas3es and the acidic nature of oxides increases.