NEETChemistryChemical Bonding and Molecular Structure
When a C ₂ molecule is converted into a C ₂⁻ ion, what is the change in its bond order and into which molecular orbital does the newly added electron enter?
Options
- ABond order increases by 0.5 and the electron enters the 2p_z orbital
- BBond order decreases by 0.5 and the electron enters the ^ * 2p_x orbital
- CBond order increases by 0.5 and the electron enters the ^ * 2p_x orbital
- DBond order decreases by 0.5 and the electron enters the ^ * 2p_z orbital
Correct answer
A. Bond order increases by 0.5 and the electron enters the 2p_z orbital
Step-by-step solution
The molecular orbital electronic configuration for C ₂ (12 electrons) is: 1s^2 , ^ * 1s^2 , 2s^2 , ^ * 2s^2 , 2p_x^2 = 2p_y^2 Its bond order is 8 - 4 2 = 2.0 . For molecules with 14 or fewer electrons, the next higher energy molecular orbital after 2p_x and 2p_y is the 2p_z orbital. When C ₂ gains an electron to form C ₂⁻ (13 electrons), the 13th electron enters the 2p_z orbital. Since 2p_z is a bonding molecular orbital, the number of bonding electrons increases by 1. The new bond order becomes 9 - 4 2 = 2.5 . The