Question

If the spin of the electrons in the excited state are parallel, it is called as:

• A. Doublet state
• B. Triplet state
• C. Singlet state
• D. Parallel state

Hint:

If the excited-state electron spins are parallel, the system is in a triplet state. If they are paired (opposite), the system is in a singlet state.

Answer 1

The Correct Option is B

Step 1: Understanding electronic spin states. When an electron in a molecule or atom gets excited, it moves to a higher energy level. The total spin of the system determines whether the state is singlet, triplet, or other multiplicities. 

Step 2: Characteristics of a triplet state. - In a singlet state, the electron spins are paired (opposite), meaning the total spin quantum number \( S = 0 \). 
- In a triplet state, the electron spins are parallel, meaning the total spin quantum number \( S = 1 \). 
- The triplet state is lower in energy than the singlet excited state because parallel spins reduce electron repulsion. 

Step 3: Why other options are incorrect. - (A) Doublet state: Applies to systems with an unpaired electron, such as free radicals. 
- (C) Singlet state: Electrons have paired spins (\( S = 0 \)), not parallel. 
- (D) Parallel state: Not a standard term in quantum chemistry.