Question

What is the valency of alluminium in ${\mathrm{Al}}_2{\mathrm{O}}_3$

Answer 1

• Aluminium has an electronic configuration as 2,8,3
• Thus the valence electron number is 3
• Aluminium has to give up those 3 electrons to attain the nearest noble gas configuration
• Oxygen has an electronic configuration as 2,6
• That means it requires 2 electrons in the outermost shell to attain the nearest noble gas configuration
• Therefore when writing symbols we interchange the valencies, ${\mathrm{Al}}^{3+}+{\mathrm{O}}^{2-}\to {\mathrm{Al}}_2{\mathrm{O}}_3$
• The valency of aluminium is 3.