Question

The ion which is isoelectronic with CO is

• A. $CN^-$
• B. $O^-_2$
• C. $N^+_2$
• D. $O^+_2$

Answer 1

Answer: (A)

$CN^-$

Answer 2

The correct option is(A): $CN^-$
An ion refers to an electronically charged atom or molecule or any species other than the neutral charge. Ion can either be positively or negatively charged. The positive charged ions are called as cation and the negative charged ions are termed as anion.
The cation is formed by the loss of electrons and the anion is formed by gain of electrons. The cation is labeled as X+ and an anion is labeled as Y- ion.
The term isoelectronic is related to the number of electrons present on the respective atom or ion. Isoelectronic species are the having same number of electrons. The number of electrons can be calculated as mentioned below:
Number of electrons in CO = 6 + 8 = 14
Number of electrons in $O_2^-$ = 16 + 1 = 17
Number of electrons in $N_2^+$ = 14 - 1 = 13
Number of electrons in $O_2^+$ = 1 6 - 1 = 15
Number of electrons in $CN^-$ = 6 + 7 + 1 = 14
Hence, CO isoelectronic with $CN^-$ ion.