Question

WHAT is the valency of - fluorine in CaF2 , Sulphur in SF6 , PHOSPHORUS in PH3 , carbon in CH4

Answer 1

(i) Fluorine in CaF₂→ (+2)+2x=0
⇒2x=-2
⇒x=-2/2
⇒x=-1
∴The valency of Fluorine in CaF₂ is '-1'.

(ii) Sulphur in SF₆→x+6(-1)=0
⇒x-6=0
⇒x=6
∴The valency of Sulphur in SF₆ is '6'.

(iii) Phosphorus in PH₃→x+3(1)=0
⇒x+3=0
⇒x=-3
∴The valency of Phosphorus in PH₃ is '-3'.

(iv)Carbon in CH₄→x+4(1)=0
⇒x+4=0
⇒x=-4
∴The valency of Carbon in CH₄ is '-4'.

Answer 2

Valency can be calculated by examining the compound.
1.
In CaF2 the valency of flourine is '-1' and that of Ca is '+2'.
2.
In SF6 the valency of sulphur is '-6' and that of flourine is '-1'.
3.
In PH3 Phosphorus P has the valency '-3' and hydrogen H has '+1'.
4.
Carbon in CH4 has the valency '-4' and that of Hydrogen H is '+1'.