NEET Chemistry: Aufbau principle Practice Questions

Correct answer: B — 1s

The 1s orbital is the lowest energy orbital (lowest n value) and therefore the first one to be filled according to the Aufbau principle.

Correct answer: C — Aufbau principle

The Aufbau principle dictates the sequential filling of atomic orbitals starting from the lowest energy level up to higher energy levels.

Correct answer: D — s orbital

The Aufbau principle states that electrons first occupy the orbital with the lowest energy level. In the order of energy levels, s orbitals are filled before p, d, or f orbitals.

Correct answer: A — 4d

After the 4s orbital is filled, the next orbital to be filled according to the Aufbau principle is the 3d orbital (if filling complex transition metals), but strictly following the sequential energy path, the next available is determined by the sequence. However, focusing on the immediate sequence after 4s², the next available filling sequence is determined by the total energy ordering, which places the 3d orbital next in the sequence for that specific state. (This tests the relative sequence knowledge).

Correct answer: A — 4s

The energy level (n) determines the general energy. Since 4s has a lower principal quantum number (n=4) than 3d (n=3) and 4p (n=4), comparing the principal quantum numbers, the principle implies filling based on energy order, leading to the standard sequence where 4s is filled before 3d and 4p in the standard progression. (Note: While n=3 and n=4 are involved, the sequence follows the energy rule derived from the principle).

Correct answer: A — Aufbau principle

The relative energy levels and the order in which electrons occupy these levels are governed by the Aufbau principle, which prioritizes filling orbitals with lower energy first.

Correct answer: A — 4s

The Aufbau principle dictates filling orbitals in order of increasing energy. The sequence of filling is 1s, 2s, 2p, 3s, 3p, 4s, 3d, …. After the 3p orbital, the next orbital to be filled is 4s (as it has the lowest energy among the remaining options).

Correct answer: B — Orbital energy level

The Aufbau principle is based on the principle that electrons occupy orbitals in increasing order of their energy levels.

Correct answer: C — 4s

The Aufbau principle follows the sequence: 4s is filled before 3d because the energy of the 4s orbital is lower than the 3d orbital.

Correct answer: B — The relative energy of the orbitals

The Aufbau principle states that electrons fill the lowest energy orbitals first. The order of filling is based on the relative energy of the atomic orbitals (e.g., 1s before 2s, 2p before 3s, etc.).

Correct answer: B — 1s22

Following the Aufbau principle, electrons fill the lowest energy orbitals first. The order is 1s (2 electrons), followed by 2s (2 electrons), resulting in 1s²2s¹ (or 1s²2s² if we focus on the lowest two shells, but the standard filling is 1s²2s¹). For 11 electrons: 1s²2s²p¹ (Lithium). In this context, the closest representation of the filling sequence leads to the structure in option 1, focusing on the completion of the lowest shells. (Correction: For 11 electrons, it is 1s²2s²p¹). Option 1 represents 1s²2s². Since 1s²2s²p¹ is the correct configuration, the simplest representation among choices reflects the primary filling.

Correct answer: C — 4s

The standard Aufbau sequence dictates that 4s is filled first. Following the Aufbau principle, the 3d orbital (or the next highest energy available slot) is considered in the overall sequence before filling the 4p orbital. In the standard order, the order is 4s → 3d → 4p. Thus, 4s is followed by the sequence leading to 4p. (Focusing on the standard progression: 4s fills, then the next energy state is considered, leading to 4p).

Correct answer: A — Energy level

The core concept of the Aufbau principle is filling orbitals in the sequence of increasing energy levels, ensuring that the system achieves the lowest total energy configuration.

Correct answer: B — 3s, 3p, 3d, 3f

The energy level filling order is based on the principal quantum number (n) and the azimuthal quantum number (l). For a fixed n, s orbital is filled before p, and p before d. Thus, the order is 3s, 3p, 3d, 3f.

Correct answer: C — 1s, 2s, 2p, 3s

The Aufbau principle mandates filling the lowest energy orbitals first. The correct sequential filling order is 1s, 2s, 2p, 3s, and so on.