Question

what are the valency atomic size and non metal and nature across the down and periodical with reasin​

Answer 1

Answer:

In a period, the number of valence electrons increases as we move from left to right side. However, in a group this periodic trend is constant, that is the number of valence electrons remains the same.

In modern periodic table metallic character increases down the group and decreases from left to right across the period.