Question

Which of the following ions does not have the same electron configuration as the noble gas neon? 

AI⁺³ 

Mg⁺² 

O^-2

F^-

S^-2

Answer 1

The electron configuration is the arrangement of electrons in space around the nucleus.

For Neon(Ne) the atomic number is 10.

Thus, the number of electrons = 10.

The electronic configuration of Ne is as follows:

1s² 2s² 2p⁶

Now,

1) For Al⁺³ :

The atomic number of Al is 13, Thus the total number of electrons for neutral aluminum is 13.

After losing 3 electrons, Al⁺³ ion is formed.

Thus, Al³⁺ contains 10 electrons.

The electronic configuration of Al⁺³ is as follows:

1s² 2s² 2p⁶

Thus, Al⁺³ ion has the same electronic configuration as the noble gas neon.

2) For Mg⁺² :

The atomic number of Mg is 12, Thus the total number of electrons for neutral magnesium is 12.

After losing 2 electrons, Mg⁺² ion is formed.

Thus, Mg⁺² contains 10 electrons.

The electronic configuration of Mg⁺² is as follows:

1s² 2s² 2p⁶

Thus, Mg⁺² ion has the same electronic configuration as the noble gas neon.

3) For O^-2 :

The atomic number of O is 8, Thus the total number of electrons for neutral oxygen is 8.

After gaining 2 electrons, O^-2 ion is formed.

Thus, O^-2 contains 10 electrons.

The electronic configuration of O^-2 is as follows:

1s² 2s² 2p⁶

Thus, O^-2 ion has the same electronic configuration as the noble gas neon.

4) For F^- :

The atomic number of F is 9, Thus the total number of electrons for neutral fluorine is 9.

After gaining 1 electron, F^- ion is formed.

Thus, F^-  contains 10 electrons.

The electronic configuration of F^-  is as follows:

1s² 2s² 2p⁶

Thus, F^- ion has the same electronic configuration as the noble gas neon.

5) For S^-2 :

The atomic number of S is 16, Thus the total number of electrons for neutral sulfur is 16.

After gaining 2 electrons, S^-2 ion is formed.

Thus, S^-2 contains 18 electrons.

The electronic configuration of S^-2 is as follows:

1s² 2s² 2p⁶ 3s² 3p⁶

Thus, S^2- ion does not have the same electronic configuration as the noble gas neon.