An element `Z` forms an oxide `ZO_(3)`.
(a) What is the valency of element `Z` ?
(b) What will be the formula of fluoride of `Z` ?

Explanation

(a) The compound `ZO_(3)` has three atoms to oxygen. Now :
Valency of one of atom = 2
So, Valency of three O atoms `= 2 xx 3`
`= 6`
Now, in the compound `ZO_(3)` the valency of Z should be equal to the total valencies of O. Since the total and the valency of element fluorine, `F`, is 1. So, the formula of fluoride of element Z should be also be 6.
(b) Formula of the fluoride of element Z.
When element Z combines with fluorine, then its fluoride is formed. Now, valency of element Z is 6 and the valency of element fluorine, F, is 1. So, the formula of floride of element Z can be worked out as follows :

Thus, the formula of fluoride of element Z is ` ZF_(6)`.
(Please note that the element Z of this problem is like sulphur element S, so that the oxide `ZO_(3)` is like sulphur trioxide, `SO_(3)`, and fluoride `ZF_(6)` is like sulphur hexafluoride , `SF_(6)`).