How many inner, outer, and valence electrons are present in an atom of each of the following elements?

(a) O (b) Sn (c) Ca (d) Fe (e) Se

(a) O = Valance Electrons (6), Inner electrons (8)

(b) Sn = Valance Electrons (2), Inner electrons (36)

(c) Ca = Valance Electrons (2), Inner electrons (20)

(d) Fe = Valance Electrons (2), Inner electrons (26)

(e) Se = Valance Electrons (6), Inner electrons (34)