Question

an element belong to 3rd period and 16th group of modern period table

Answer 1

1) Since the element belongs to group 16, therefore its electronic configuration is 2, 8, 6, and hence it has 6 valence electrons. Its valency is 8 – 6 = 2 (-2). 

2) Molecular formula is XH2
..
Electron dot structure. ..X..

3) Element X is Sulphur. It is non metallic

Answer 2

Element belongs to 3rd period, therefore 3 shells are and 6A group, therefore 6 number of valence electrons.
So the element is sulfur which has 3 shells and 6 valence electrons.