Please help me with 17 & 18!!
Thankss in advance!! :)

#17
#a
Group 15 elements have valency 3
#b
Let's check the EC of both
[tex]\\ \rm\Rrightarrow [O]=1s^22s^22p^4[/tex]
[tex]\\ \rm\Rrightarrow [S]=[Ne]3s^23p^4[/tex]
#c
Decrease in size
#18
#a
#b
#c