Question

The ion that is isoelectronic with CO is

• A. \( \text{O}_2^+ \)
• B. \( \text{CN}^- \)
• C. \( \text{O}_2^- \)
• D. \( \text{N}_2^+ \)

Hint:

To determine if two species are isoelectronic, compare their total number of electrons. Species with the same number of electrons are isoelectronic.

Answer 1

The Correct Option is B

To determine which ion is isoelectronic with carbon monoxide (CO), we need to first find the number of electrons in each species. Isoelectronic species have the same number of electrons.

CO is composed of one carbon atom and one oxygen atom. Carbon (C) has an atomic number of 6, and oxygen (O) has an atomic number of 8. Therefore, the total electron count in CO is:

Total electrons in CO = \(6 \text{ (carbon)} + 8 \text{ (oxygen)} = 14\) electrons.

Let's analyze each option:

1. \( \text{O}_2^+ \)
Oxygen molecule \( \text{O}_2 \) has \( 8 + 8 = 16 \) electrons. Loss of one electron (indicated by \( + \)) gives:
Total electrons in \( \text{O}_2^+ \) = 16 - 1 = 15 electrons.

2. \( \text{CN}^- \)
Cyanide ion \( \text{CN}^- \) consists of carbon (6 electrons) and nitrogen (7 electrons) with an additional electron due to the negative charge:
Total electrons in \( \text{CN}^- \) = 6 + 7 + 1 = 14 electrons.

3. \( \text{O}_2^- \)
\( \text{O}_2 \) molecule again starts with 16 electrons. With an additional electron (indicated by \( - \)):
Total electrons in \( \text{O}_2^- \) = 16 + 1 = 17 electrons.

4. \( \text{N}_2^+ \)
\( \text{N}_2 \) molecule consists of \( 7 + 7 = 14 \) electrons. Loss of one electron (indicated by \( + \)) gives:
Total electrons in \( \text{N}_2^+ \) = 14 - 1 = 13 electrons.

Thus, the ion with the same number of electrons as CO (14 electrons) is \( \text{CN}^- \).

Answer 2

Isoelectronic species have the same number of electrons. The electron configuration of \( \text{CO} \) is: - Carbon (C) has 6 electrons, and Oxygen (O) has 8 electrons.
- \( \text{CO} \) has a total of \( 6 + 8 = 14 \) electrons. Now, let's examine the options:
- \( \text{O}_2^+ \) has 15 electrons (Oxygen in \( \text{O}_2^+ \) loses one electron).
- \( \text{CN}^- \) has 14 electrons (Carbon has 6 electrons and Nitrogen has 7 electrons, plus the extra electron from the negative charge, making a total of 14 electrons).
- \( \text{O}_2^- \) has 17 electrons (Oxygen has 8 electrons per atom, plus an extra electron from the negative charge, totaling 17).
- \( \text{N}_2^+ \) has 13 electrons (Nitrogen has 7 electrons per atom, minus one due to the positive charge).
Thus, the ion that is isoelectronic with \( \text{CO} \) is \( \text{CN}^- \), which has 14 electrons.
Thus, the correct answer is \( \text{CN}^- \).