Which atom in the ground state has five electrons in its outee level and ten electrons in its kernel (1) C (2) Cl (3) Si (4) P

If you use its electronic structure the last number should be a five so something like (2,5), (2,8,5) or (2,8,8,5) etc.

The elements therefore with 5 as it's final number and 5 on the outer orbit are N, P, As, Sb, Bi, Uup. Therefore with the answers given to you the answer is most likely 4) Phosphorus.