Question

An element is represented by ${}_Z{X}^A$, where Z is atomic number which is also equal to number of proton, A is mass number and X is symbol of the element.
Mass number (A) = Number of protons (Z) + Number of neutrons.
Isoelectronic: Species/ elements having same number of electron
Isodiaphers: Elements having same value of $|(A-2Z)|$
Isotopes: Atoms having same number of proton


Which of the following species is isoelectronic with the hydride ion?

• A. $L{i}^{+}$
• B. $H{e}^{+}$
• C. $L{i}^{2+}$
• D. $B{e}^{+}$

Answer 1

The correct option is A $L{i}^{+}$

Isoelectronic species are those which have the same number of electrons.
Hydride ion $\left(H^{-}\right)$ contains 2 electrons. The $L{i}^{+}$ atom also contains 2 electrons. Hence, they are isoelectronic.