Question

Which of the following is/are correct with respect to the energy of atomic orbitals of a hydrogen atom? 
(A) \( 1s<2s<2p<3d<4s \) 
(B) \( 1s<2s = 2p<3s = 3p \) 
(C) \( 1s<2s<2p<3s<3p \) 
(D) \( 1s<2s<4s<3d \) 
Choose the correct answer from the options given below:

• (A) and (C) only
• (A) and (B) only
• (C) and (D) only
• (B) and (D) only

Hint:

Remember that the energy of orbitals increases with the principal quantum number, but for orbitals within the same shell, the order depends on the angular quantum number (l).

Answer 1

The Correct Option is A

For hydrogen-like atoms, orbital energy increases with the principal quantum number (n). Within a given shell (same n), orbitals with higher angular momentum (l) possess greater energy.  
- (A) is correct, accurately ordering orbitals as \( 1s<2s<2p<3d<4s \). 
- (B) is incorrect because \( 2s eq 2p \) and \( 3s eq 3p \). 
- (C) is correct, adhering to the established orbital energy order for hydrogen. 
- (D) is incorrect; the ordering is flawed as \( 4s \) has lower energy than \( 3d \). 
Consequently, (A) and (C) are the correct responses.