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

The energy ordering of orbitals for hydrogen-like atoms is governed by the principle that the energy increases as the principal quantum number (n) increases, but within the same shell, orbitals with higher angular momentum (l) have higher energy. 
- (A) is correct as it correctly orders the orbitals: \( 1s<2s<2p<3d<4s \). 
- (B) is incorrect as \( 2s \neq 2p \), and \( 3s \neq 3p \). 
- (C) is correct as it follows the correct ordering of orbitals for hydrogen. 
- (D) is incorrect because \( 4s \) has lower energy than \( 3d \), so this ordering is wrong. 
Therefore, the correct answers are (A) and (C).