a. a main group element with the valence electron configuration 3s23p1 is in periodic group fill in the blank 1 . it forms a monatomic ion with a charge of fill in the blank 2 . b. a main group element with the valence electron configuration 2s22p4 is in periodic group fill in the blank 3 . it forms a monatomic ion with a charge of fill in the blank 4 .