Question

what is the need to classfy element on the basis that the atomic size and valencyincreases from left to right in the periodic table?​

Answer 1

There is no need to classify elements on the basis of atomic size just Mendeleev did it so in his periodic table.

Valency first increases then decreases from left to right in a periodic table because the size of the atom changes and is the least in the rightmost.

Brainliest if satisfied

Answer 2

Valency:-

The valency of an element is determined by the number of valence electrons present in the outermost shell. In a Group, all the elements have the same number of valence electrons. On moving from left to right in each short period, the valency increases from 1 to 4 and then decreases to zero.

Atomic Size:-

In a period, atomic number decreases from left to right. This is because the electrons are added to the same shell so they experience a greater pull from the nucleus.

HOPE IT HELPED.