Answer
a) $BaO$
b) $Ca_{3}P_{2}$
c) $Al_{2}S_{3}$
d) $Li_{3}N$
Work Step by Step
a) Barium is an alkaline earth metal with a tendency to lose 2 electrons and oxygen is an electronegative nonmetal with a tendency to accept 2 electrons. Thus two elements have valency 2 and hence the formula is $BaO$
b) Calcium is an alkaline earth metal with a tendency to lose 2 electrons and oxygen is a nonmetal with a tendency to accept 3 electrons. Thus Ca and P have valencies 2 and 3 respectively. Therefore the formula is $Ca_{3}P_{2}$
c) Aluminium is a Group 3A metal with a tendency to lose 3 electrons and Sulfur is a nonmetal with a tendency to accept 2 electrons. Thus Al and S have valencies of 3 and 2 respectively. Therefore the formula is $Al_{2}S_{3}$
d) Lithium is an alkali metal with a tendency to lose 1 electron and Nitrogen is an electronegative nonmetal with a tendency to accept 3 electrons. Thus Ca and P have valencies 2 and 3 respectively. Therefore the formula is $Li_{3}N$
