- Atomic number: 9

- Electronic configuration: 1s² 2s² 2p⁵

- Outer shell (valence shell): 2p⁵

- Number of electrons in the outer shell: 5

Chlorine (Cl)

- Atomic number: 17

- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁵

- Outer shell (valence shell): 3p⁵

- Number of electrons in the outer shell: 5