Question

Account for the fact that the fourth period has 18, not 8 elements.

AND

An element is present in the third period of p-block. It has 5 electrons in its outermost
shell. Predict its group. How many unpaired electrons does it have?

Answer 1

Explanation:

because from the 3 period all periods have 18 elements and hence they how they follow the octet rule and oxidation states.

and

the element is arsenic and its present in group 15 or Va group and have 3 unpaired electrons