Question

The ion which is isoelectronic with CO is

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

Hint:

An ion is an atom or a molecule which has a net electric charge. The charge on the atom can be either positive or negative.

Answer 1

The Correct Option is A

To answer the question, "Which ion is isoelectronic with CO?", we need to identify ions or molecules that have the same number of electrons as carbon monoxide (CO).

Firstly, let's determine the number of electrons in CO:

1. Carbon (C) is in group 14 of the periodic table and has an atomic number of 6, which means it has 6 electrons.
2. Oxygen (O) is in group 16 and has an atomic number of 8, giving it 8 electrons.
3. Therefore, the molecule CO has a total of \(6 + 8 = 14\) electrons.

We need to find the ion among the given options that also has 14 electrons, making it isoelectronic with CO. Let's examine each option:

1. CN^−: The cyanide ion consists of carbon and nitrogen.
   • Carbon (C): 6 electrons.
   • Nitrogen (N): 7 electrons.
   • The negative charge (−1) indicates an additional electron.
   • Total electrons: \(6 + 7 + 1 = 14\).
2. O_2^−: The superoxide ion consists of two oxygen atoms.
   • Each Oxygen (O): 8 electrons. Total for two atoms = \(2 \times 8 = 16\).
   • The charge (−1) provides an additional electron.
   • Total electrons: \(16 + 1 = 17\) (This is not 14).
3. N_2^+: An ion of nitrogen molecule.
   • Each Nitrogen (N): 7 electrons. Total for two atoms = \(2 \times 7 = 14\).
   • The positive charge (−1) indicates the loss of one electron.
   • Total electrons: \(14 - 1 = 13\) (This is not 14).
4. O_2^+: An ion of oxygen molecule.
   • Each Oxygen (O): 8 electrons. Total for two atoms = \(2 \times 8 = 16\).
   • The positive charge (−1) indicates the loss of one electron.
   • Total electrons: \(16 - 1 = 15\) (This is not 14).

Among the options, CN^− is the only ion that has the same number of electrons (14) as CO, making it isoelectronic with CO.

Therefore, the ion that is isoelectronic with CO is CN^−.