Pick out among the following species isoelectronic with CO₂

Solution

To determine which species is isoelectronic with CO₂, we calculate the total number of electrons in each species and compare them to the number of electrons in CO₂.

Step 1: Count the total electrons in CO₂

• Carbon (C): 6 electrons
• Oxygen (O): 8 × 2 = 16 electrons
• Total electrons in CO₂: 6 + 16 = 22 electrons

Step 2: Calculate the total electrons for each species

(A) N₃^-

• Nitrogen (N): 7 × 3 = 21 electrons (for three nitrogen atoms)
• The negative charge (-1): adds 1 extra electron
• Total electrons: 21 + 1 = 22

Thus, N₃^- has 22 electrons and is isoelectronic with CO₂.

(B) CNO^-

• Carbon (C): 6 electrons
• Nitrogen (N): 7 electrons
• Oxygen (O): 8 electrons
• The negative charge (-1): adds 1 extra electron
• Total electrons: 6 + 7 + 8 + 1 = 22

Thus, CNO^- has 22 electrons and is isoelectronic with CO₂.

(C) NCN^2-

• Nitrogen (N): 7 × 2 = 14 electrons (for two nitrogen atoms)
• Carbon (C): 6 electrons
• The negative charge (-2): adds 2 extra electrons
• Total electrons: 14 + 6 + 2 = 22

Thus, NCN^2- has 22 electrons and is isoelectronic with CO₂.

Final Answer

The correct options are:

• (A) N₃^-
• (B) CNO^-
• (C) NCN^2-

All three species are isoelectronic with CO₂, as they have 22 electrons each.