What is a valence electron? How many valence electrons does an element in Group 2 have? Group 18?
A valance electron is an electron that is the outer shells and can be used for bonding
Group 2 has two valance electrons.
Group 18 would have 8 valance electrons.
( The 10 d electrons will drop down into the next lower shell and are not longer in the outermost shell and are no longer available for bonding. )
18- 10 = 8