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

(N/A) Lithium $(Li)$ has a valency of $1$ and oxygen $(O)$ has a valency of $2$. The formula is $Li_2O$.
$(b)$ Magnesium $(Mg)$ has a valency of $2$ and nitrogen $(N)$ has a valency of $3$. The formula is $Mg_3N_2$.
$(c)$ Aluminium $(Al)$ has a valency of $3$ and iodine $(I)$ has a valency of $1$. The formula is $AlI_3$.
$(d)$ Silicon $(Si)$ has a valency of $4$ and oxygen $(O)$ has a valency of $2$. The formula is $SiO_2$.
$(e)$ Phosphorus $(P)$ can show valencies of $3$ or $5$ and fluorine $(F)$ has a valency of $1$. The formulas are $PF_3$ or $PF_5$.
$(f)$ The element with atomic number $71$ is Lutetium $(Lu)$,which has a valency of $3$. Fluorine $(F)$ has a valency of $1$. The formula is $LuF_3$.