Predict the formula of the stable binary compounds that would be formed by the combination of the following pairs of elements.
Question:

Predict the formula of the stable binary compounds that would be formed by the combination of the following pairs of elements.

(a) Lithium and oxygen

(b) Magnesium and nitrogen

(c) Aluminium and iodine

(d) Silicon and oxygen

(e) Phosphorus and fluorine

(f) Element 71 and fluorine

Solution:

(a) $\mathrm{Li}_{2} \mathrm{O}$

(b) $\mathrm{Mg}_{3} \mathrm{~N}_{2}$

(c) $\mathrm{All}_{3}$

(d) $\mathrm{SiO}_{2}$

(e) $\mathrm{PF}_{3}$ or $\mathrm{PF}_{5}$

(f) The element with the atomic number 71 is Lutetium (Lu). It has valency 3 . Hence, the formula of the compound is $L u F_{3}$.