Why do the Group I metals have a change of
positive one (+1)?

Explanation:

The +1 is their oxidation sate and this implies that the love to form bonds where they can lose one of their electrons.

The positive value indicates that an atom has lost an electron.

Group elements have one electron in their outermost shell. If they lose this one electron, they become isoelectric with the nearest noble gases and this imparts a stability on the atom.

So, group 1 elements have an oxidation state of +1

2b2t

explanation:

2b2t