Question

The position of three elements A, B and C in the periodic table is shown
below :
Group 
Period ↓
I II III IV V VI VII VIII
1
2 C
3 A B
Giving reasons explain :
(a) Element A is a metal.
(b) Element B has larger atomic size than the element C.
(c) Element C has a valency of one

Answer 1

element a is a metal because it will have 3 electrons in its outermost shell so it will loose those 3 electrons and will become positively charged so it is a metal.

(2) as the number of shells increases on going down in a group so the radius of atom will also increase so element b will have larger atomic size than c.

(3) an atom can have valency 1 if it has either only one electron in its outermost shell or it has 7 electrons in the outermost shell.
if it has 1 electron in outermost shell than the atom will loose that electron but if it has 7 electrons then it will gain one electron to complete its octet.

hope it helps.

Answer 2

for answer pls see the attachment