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

Explanation

(a) Lithium is an alkali metal ( Group 1). It has only one electron in the valence shell, therefore its valence is 1. Oxygen is a group 16 element with a valence of 2. Therefore . Formula of the compound formed would be `Li_(2)O` ( lithium oxide) .
( b) Magnesium is an alkaline earth metal ( group 2) and hence has a valence of 2. Nitrogen is a group 15 element with a valence of 8-5 =3. Thus the formula of the compound formed would be `Mg_(3)N_(2)` (magnesium nitride )
( c) Aluminium is group 13 element with a valence of 3 while iodine is a halogen ( group 17) with a valence of 1. Therefore the formula of the compound formed would be `A1I_(3)` ( aluminium iodine ).
( d) Silicon is a group 14 element with a valence of 4 while oxygen is a group 16 element with a valence of 2 . Hence the formula of the compound formed is `SiO_(2)` ( silicon dioxide)
( e) Phosphorus is a group 15 element with a valence of 3 or 5 while fluorine is a group 17 element with a valence of 1. Hence the formula 71 is a lanthanoid called lutetium (Lu). Its common valence is 3.
Fluorine is a group 17 ( halogen ) element with a valence of 1. Therefore the formula of the compound formed would be `LuF_(3)` ( lutetium fluoride).