Question

$A,B,C,D$ are the elements having an atomic number $13,17,20,8$.Given the formula formed between
1. A and B
2.C and D

Answer 1

Solution:-

Electronic configuration of element A with atomic no. 13 $=2,8,3$

Electronic configuration of element B with atomic no. 17$=2,8,7$

Electronic configuration of element C with atomic no. 20$=2,8,8,2$

Electronic configuration of element D with atomic no. 8$=2,6$

Valency of an element-

• $n$ for $n\le 4$
• $8-n$ for $n\ge 4$

whereas, n = no. of electrons in outermost shell

1. Formula between element A and B-

Valency of element $A=3(\because n\le 4)$

Valency of element $B=8-7=1(\because n\ge 4)$

$\therefore$ For formula between A and B- $A{B}_3$

2. Formula between element C and D-

Valency of element $C=2(\because n\le 4)$

Valency of element $B=8-6=2(\because n\ge 4)$

$\therefore$ For formula between C and D- $C_2{D}_2\equiv CD$