chemistry help?

Question

if electronic configuration of element is [xe]54 6S2 4F14 5D1then what will be its valency and what will its reaction and product with aluminium

Answer 1

Look at the s and p orbitals this will tell you the valence of the atom. In this case 2 electrons in the 6s means it probally has a +2 valence.
In reality this element is La and has a +3 charge. The single electron in the 5d orbital is combined for a more stable arrangement with the 6s electrons. Thus the +3 charge. This is an exception rather than the rule for finding valances.