Question

Alkali metals are poor completing agent

Answer 1

The best answer I have is they don’t have D orbital electrons like transition metals. They don’t tend to share their S orbital electrons, because they are relatively easy to strip so they form positive ions. They bond to other atoms then by an ionic bond. Transition metals have the d orbital electrons as well as empty orbits, so they can make coordination bonds where the electrons get shared. It’s not strong like a direct covalent bond or an ionic bond. But it does allow them to make coordination bonds to multiple adjacent atoms, so they form complexes.

Answer 2

They don't have D orbital electrons like transition metals.They don't tend to share their S orbital electrons, because they are relatively easy to strip so they form positive ions. They bond to other atoms then by an ionic bond. Transition metals have the D orbital electrons as well as empty orbits, so they can make coordination bonds where the electrons get shared. It's not strong like a direct co-valent bond or an ionic bond. But it does allow them to make coordination bonds to multiple adjacent atoms, so they form complexes.