Case one: ns is half-filled and (n-1)d is less than full. Is valence 1+number of electrons in (n-1)d or number of electrons in (n-1)d or 1? Case two: ns is fully filled and (n-1)d is less than full Is valence 2 or 2+ number of electrons in (n-1)d or number of electrons in (n-1)d? Case three, ns is fully filled, and (n-1)d is full is valence 12 or 2 or 10? Case four: ns is half-filled, and (n-1)d is full. is valence 1 or 1+10 or 10?