Question

atoms tend to gain,lose,and share valence electrons until each atom had the same number of valence electrons as the

Answer 1

That's a wide open question. What choices do you have?

Answer 2

outermost shell holds maybe ?
like maybe
If the outer shell holds 8, like Li to Ne, the second row in the periodic table
Li can lose one (Li+) to leave none in shell 2 and leave the inner shell which holds 2 when full
F has 7 but the outer shell holds 8 so it wants to grab one and become F-
Ne gas is noble and has exactly 8 in that outer shell so is happy and does not want to grab or lose any.