Question

Which electron shell contains the valence electrons of a radium atom in the ground state?

(1) the sixth shell (2) the second shell
(3) the seventh shell (4) the eighteenth shell

Answer 1

(3) the seventh shell

Step-by-step explanation:

Let's consider the electron configuration of radium in the ground state.

₈₈Ra: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s²

As we can see, the valence electrons are in the 7s shell, that is, the seventh shell. These are the electrons that participate in bonds.