Question

Neutral atoms of neon (atomic number 10) have the same number of electrons as each of the following except:

Answer 1

Answer : The correct option is, Ar

Explanation :

(1) The element is, $Na^+$

Atomic number of Na = 11

The general electronic configuration of Na is, $1s^22s^22p^63s^1$

The electronic configuration of $Na^+$ is, $1s^22s^22p^6$

The number of electrons in $Na^+$ = 10

(2) The element is, $Mg^{2+}$

Atomic number of Mg = 12

The general electronic configuration of Mg is, $1s^22s^22p^63s^2$

The electronic configuration of $Mg^{2+}$ is, $1s^22s^22p^6$

The number of electrons in $Mg^{2+}$ = 10

(3) The element is, $F^-$

Atomic number of F = 9

The general electronic configuration of F is, $1s^22s^22p^5$

The electronic configuration of $F^-$ is, $1s^22s^22p^6$

The number of electrons in $F^-$ = 10

(4) The element is, Ar

Atomic number of Ar = 18

The general electronic configuration of Ar is, $1s^22s^22p^63s^23p^6$

The number of electrons in Ar = 18

(5) The element is, $O^{2-}$

Atomic number of O = 8

The general electronic configuration of O is, $1s^22s^22p^4$

The electronic configuration of $O^{2-}$ is, $1s^22s^22p^6$

The number of electrons in $O^{2-}$ = 10

From this we conclude that, the option 1, 2, 3 and 5 have the same number of electrons as the neutral atom of neon. While in 'Ar' there are 18 number of electrons.

Hence, the correct option is, Ar

Answer 2

The answer would be : Ar.

Hope this helps !

Photon