Answer to Question #271412 in General Chemistry for Del

Question

Write electron configurations for the following chemical species. Then, give which the noble gas has the same

configuration.

1. Na +

2. Mg +2

3. I -

4. Se- 2

5. Mn +7

Answer 1

1. Na +

[Ne] 3s¹

2. Mg +2

Mg2+ has an electronic configuration of 1s² 2s² 2p^6, i.e., has a total number of 10 electrons similar to that of a Noble gas [Ne] instead of Mg 12 as its total number of electrons and configuration of 1s² 2s² 2p6 3s².

3. I -

Electron configuration: [Kr] 4d¹⁰5s²5p⁵

4. Se- 2

The electron configuration for a Se2- ion is [Ar] 4s2 3d10 4p6 or simply [Kr].

5. Mn +7

The ground state electron configuration of ground state gaseous neutral manganese is [Ar]. 3d5. 4s2

Since our sodium atom has lost a negatively charged electron, it becomes a positively charged sodium ion: Na⁺. This sodium ion, with one electron fewer than the sodium atom, has the same electron configuration as the noble gas neon and is chemically stable.