Why is the maximum covalence of B 4?
Boron doesn't have a d-orbital. So, it cannot extend its covalence beyond 4 while Aluminum and other elements have d-orbitals and thus, they are expected to have maximum covalence beyond 4.
The maximum covalence of the first member of each group is:
Why does carbon not form C2 atom with 4 covalent bonds ? When it form 3 covalent bonds then why not 4 bonds.