What does the Aufbau principle state?
A
Electrons fill higher energy orbitals first
B
Electrons fill orbitals randomly
C
Electrons fill orbitals starting from the lowest energy level
D
Electrons avoid lower energy orbitals
Analysis & Theory
The Aufbau principle states that electrons fill orbitals in the order of increasing energy, starting from the lowest energy level.
According to the Aufbau principle, which orbital is filled **after 3p**?
Analysis & Theory
After 3p, the next orbital filled is 4s, because it has lower energy than 3d.
Which of the following orbital filling orders is correct based on the Aufbau principle?
A
1s → 2s → 2p → 3s → 3p → 4s → 3d
B
1s → 2s → 3s → 2p → 3p → 4s
Analysis & Theory
The correct order is 1s → 2s → 2p → 3s → 3p → 4s → 3d.
Why does the 4s orbital fill before the 3d orbital?
A
4s is closer to the nucleus
B
4s has lower energy than 3d
Analysis & Theory
Though 4s is in a higher principal shell, it has lower energy than 3d, so it fills first.
Which rule complements the Aufbau principle by requiring opposite spins in the same orbital?
C
Pauli Exclusion Principle
Analysis & Theory
The Pauli Exclusion Principle states that no two electrons in the same orbital can have the same spin.
What is the electron configuration of **Nitrogen (atomic number 7)** based on the Aufbau principle?
Analysis & Theory
Nitrogen has 7 electrons: 1s² 2s² 2p³ following Aufbau principle.
Which element violates the expected Aufbau order due to stability of half-filled orbitals?
Analysis & Theory
Copper has an exceptional configuration: [Ar] 4s¹ 3d¹⁰ for extra stability of a full d-subshell.
What is the correct order of filling for the 4f and 5d orbitals?
Analysis & Theory
4f is filled before 5d according to the energy levels in the Aufbau sequence.
How many electrons can the 3d orbital hold?
Analysis & Theory
The d-subshell has 5 orbitals, each holding 2 electrons, so a total of 10 electrons.
What is the complete electron configuration of Oxygen (Z = 8) based on Aufbau filling?
Analysis & Theory
Oxygen has 8 electrons: 1s² 2s² 2p⁴ according to the Aufbau principle.