Chemistry Q51 – JEE-MAIN 2025

Home Chemistry Structure of AtomQuestion #622

Consider the ground state of chromium atom (Z=24). How many electrons are with Azimuthal quantum number

l = 1

and

l = 2

respectively ?

Clue 1 of 3: Electron Configuration

Determine the ground state electron configuration of Chromium (Z=24), remembering its exception to the Aufbau principle.

🥷

Ninja Strategy•Chromium Exception and Quantum Number Mapping

Recognize Chromium's electron configuration exception ( $3 d^{5} 4 s^{1}$ ) and correctly map $l = 1$ to p-orbitals and $l = 2$ to d-orbitals to count electrons.

🧠 Full Solution Path

Step 1: Determine the ground state electron configuration of Chromium (Z=24).✦ Active

The ground state electron configuration for Chromium (Z=24) is $[A r] 3 d^{5} 4 s^{1}$ . This is an exception to the Aufbau principle, where one electron from the $4 s$ orbital moves to the $3 d$ orbital to achieve a more stable half-filled $3 d$ subshell. The full configuration is $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{5} 4 s^{1}$ .

Step 2: Identify electrons with azimuthal quantum number

l = 1

.○ Expand

The azimuthal quantum number $l = 1$ corresponds to p-subshells. From the electron configuration:

- $2 p^{6}$ contributes 6 electrons.

- $3 p^{6}$ contributes 6 electrons.

Total electrons with $l = 1 = 6 + 6 = 12$ .

Step 3: Identify electrons with azimuthal quantum number

l = 2

.○ Expand

The azimuthal quantum number $l = 2$ corresponds to d-subshells. From the electron configuration:

- $3 d^{5}$ contributes 5 electrons.

Total electrons with $l = 2 = 5$ .

Therefore, the number of electrons with $l = 1$ and $l = 2$ are 12 and 5 respectively.

✦ STEM Console utilizes AI models to generate step-by-step explanations and math clues. AI can make mistakes.

Chemistry Question 51 – JEE-MAIN 2025

Clue 1 of 3: Electron Configuration

🧠 Full Solution Path