Four elements P,Q,R and S have 1,2,3, and 7 electrons in their outermost shells respectively. The element which is unlikely to be a metal is?

Element P has only 1 electron in its outermost shell, which is highly reactive, and it is easier for P to lose this electron than to gain 7 electrons to fill its outermost shell. Therefore, P is highly likely to be a metal. Element Q has 2 electrons in its outermost shell, and it is relatively easy for it to lose 2 electrons and form a cation. Therefore, Q is also highly likely to be a metal. Element R has 3 electrons in its outermost shell, and it is relatively easy for it to lose 3 electrons and form a cation. Therefore, R is also highly likely to be a metal. Element S has 7 electrons in its outermost shell, which is close to a full shell with 8 electrons. It is easier for S to gain 1 electron and form an anion rather than lose 7 electrons to form a cation. Therefore, S is unlikely to be a metal. Hence, the answer is S.