Aufbau principle, Pauli exclusion principle and Hund's rule — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The Pauli exclusion principle states that no two electrons in an atom can have

• A. the same set of all four quantum numbers
• B. the same principal quantum number
• C. opposite spins
• D. the same orbital angular momentum quantum number

Question 2 · difficulty L2 · understanding

According to the Aufbau principle, electrons occupy orbitals in order of

• A. increasing energy
• B. decreasing energy
• C. increasing atomic mass
• D. random energy

Question 3 · difficulty L2 · understanding

Hund's rule states that electrons occupy degenerate orbitals

• A. singly with parallel spins before pairing
• B. in pairs immediately
• C. with opposite spins in separate orbitals only
• D. randomly with no spin preference

Question 4 · difficulty L2 · understanding

The maximum number of electrons in one orbital is

• A. 2
• B. 1
• C. 4
• D. 6

Question 5 · difficulty L3 · application

Which ground-state arrangement is correct for two electrons in the three degenerate p orbitals?

• A. Two separate p orbitals with parallel spins
• B. Both electrons paired in one p orbital
• C. Two separate orbitals with opposite spins only
• D. One electron in p and one in a higher d orbital

Question 6 · difficulty L3 · application

What is the ground-state electron configuration of carbon, Z = 6?

• A. $1s^2 2s^2 2p^2$
• B. $1s^2 2s^1 2p^3$
• C. $1s^2 2p^4$
• D. $1s^2 2s^2 3s^2$

Question 7 · difficulty L3 · application

How many unpaired electrons are present in the ground-state $2p^3$ configuration?

• A. 3
• B. 2
• C. 1
• D. 0

Question 8 · difficulty L3 · application

Which orbital filling violates the Pauli exclusion principle?

• A. Two electrons in the same orbital with the same spin
• B. Two electrons in different orbitals with parallel spins
• C. One electron in each of three p orbitals
• D. Two electrons in one orbital with opposite spins

Question 9 · difficulty L4 · application

According to the usual $(n+l)$ rule, which orbital fills before 3d?

• A. 4s
• B. 4p
• C. 5s
• D. 4d

Question 10 · difficulty L4 · application

What is the correct distribution of four electrons among three degenerate p orbitals in a ground-state atom?

• A. One orbital paired and two singly occupied
• B. Two orbitals paired and one empty
• C. All four in one orbital
• D. One electron in each orbital and the fourth in a higher shell