Explain about the general characteristics of periods.

Explanation

(i) Number of electrons in outermost shell: The number of electrons present in the outermost shell increases from 1 to 8 as we proceed in a period.
(ii) Number of shells: As we move from left to right in a period the shells remains the same. The number of shells present in the elements corresponds to the period number. For exampleall the elements of 2nd period have on `2^(nd)` shells (K, L)
(iii) Valency: The valency of the elements increases from left to right in a period. With respect to hydrogen, the valency of period elements increases from 1 to 4 and then falls to one. With respect to oxygen, the valency increases from 1 to 7.
(iv) Metallic character: The metallic character of the elements decreases across a period.
For example : `3^(rd)` period`ubrace(Na Mg Al)_("Metals")ubrace(Si P S Cl)_("Non-metals")`