Question

Li+ is isoelectronic with which of the following ions?
(1) H+
(2) Na+
(3) B3+
(4) He+​

Answer 1

$Li^{+}$ is isoelectronic with (3) $B^{3+}$.

Let us see, why $Li^{+}$ is isoelectronic with $B^{3+}$

Cations or anions or atoms having same number of electrons but different magnitude of nuclear charge are called isoelectronic species.

Number of electrons in Li = 3

When Li loses one electron it becomes a cation i.e.,  $Li^{+}$

Number of electron in $Li^{+}$ = (3-1) = 2

Now, checking the number of electrons of the species given in option-

1. Number of electrons in $H^{+}$  = (1-1) = 0
2. Number of electrons in $Na^{+}$ = (11-1) = 10

   3. Number of electrons in $B^{3+}$ = (5-3) = 2

    4. Number of electrons in $He^{+}$ = (2-1) = 1

∴ Number of electrons in $B^{3+}$ and $Li^{+}$ are same.

Thus, $Li^{+}$ is isoelectronic with $B^{3+}$.

Answer 2

$Li+$ is isoelectronic with $B3+$ ions

Option (c) is the correct answer

Explanataion :-

• $Li+$ is isoelectronic with $B3+$ ions

• Isoelectronic species are cations and anions which have the same number of electrons but they have a different value of nuclear charge
• The Number of electrons in Lithium is  = 3
• When Lithium Li loses one electron it will become a cation.
• Number of electron in Li ion will be  = (3-1) = 2
• Now,we will be checking the number of electrons of the species given in option-
• (a)$H+$ ion -- Number of electrons in   = (1-1) = 0
• (b) $Na+$ion --Number of electrons in  = (11-1) = 10
• (c) $B 3+$ion -- Number of electrons in  = (5-3) = 2
• (d) $He+$ ion -- Number of electrons in  = (2-1) = 1
• Here in option (c) is the correct answer because the number of electrons are same.