Answer
a) $Li_{2}O$
b) $K_{2}Se$
c) $MgBr_{2}$
Work Step by Step
a) Lithium has 1 valence electron, and oxygen needs 2 in order to achieve a stable configuration, so therefore the formula of the compound is $Li_{2}O$
b) Potassium has 1 valence electron, and selenium needs 2 in order to achieve a stable configuration, so therefore the formula of the compound is $K_{2}Se$
c) Magnesium has 2 valence electrons, and bromine needs 1 in order to achieve a stable configuration, so therefore the formula of the compound is $MgBr_{2}$
