Question

Which of the following pairs contains duplet and octet configuration respectively in the
valence shell?
(a) Ne, Ar
(b) Mg+^2, Be+^2
(c)ca+^2,o-^2
(d)Li+^1,N-^3​

Answer 1

Answer:

Ne has 10 electron in the valence shell.

Answer 2

The answer is option d)$Li^{+}, N^{3-}$

Explanation:

The question is asking to find the pair having a duplet and octet configuration respectively. That is the first species should have a duplet configuration and the second the octet configuration.

• Duplet configuration means 2 electrons in the valence shell, and
• Octet configuration means 8 electrons in the valence shell.

Now, let us look at the options:

$Ne, Ar:$

• Neon and Argon both are noble gases, hence, both contain an octet configuration in the outermost shell.
• Hence, this option is not correct.

$Mg^{2+}, Be^{2+}:$

• Mg and Be are both group 2 elements, having two valence electrons, but after the loss of two electrons, they form the cations which contain an octet configuration$(Mg^{2+})$ and a duplet configuration$(Be^{2+})$ in the outermost shell.
• Hence, this option is also not correct.

$Ca^{2+}, O^{2-}:$

• Calcium is a member of group 2, and after the loss of two electrons, it acquires an octet configuration.
• Oxygen is a member of group 16, and after the gain of two electrons to form an oxide, it also achieves an octet configuration.
• Hence, this option is not correct.

$Li^{+}, N^{3-}:$

• Lithium is a Group 1 element with one valence electron and atomic number 3. After the loss of one electron, it has two electrons in the outermost shell, which is a duplet configuration.
• Nitrogen has 5 valence electrons. On accepting three electrons to form nitride ions, it acquires an octet configuration.
• Hence, this option is correct.