Question

The number of electrons with azimuthal quantum numbers \( l = 1 \) and \( l = 2 \) for Cr in the ground state electronic configurations are respectively. [Given: Cr (Z = 24)]

• A. 5 and 16
• B. 12 and 5
• C. 12 and 8
• D. 12 and 16

Hint:

Remember: \( l = 0 \) (s), \( l = 1 \) (p), \( l = 2 \) (d), \( l = 3 \) (f)Count electrons from the electronic configuration accordingly.

Answer 1

The Correct Option is B

Step 1: Write the electronic configuration of Cr.
Atomic number of chromium = 24.
The ground state electronic configuration is:
\[ [Ar]\, 3d^5\, 4s^1 \]
Expanded form:
\[ 1s^2\, 2s^2\, 2p^6\, 3s^2\, 3p^6\, 3d^5\, 4s^1 \]

Step 2: Identify electrons with \( l = 1 \) (p-orbitals).
For \( l = 1 \), electrons are in p-orbitals.
p-orbitals present are:
\[ 2p^6,\; 3p^6 \]
Total electrons:
\[ 6 + 6 = 12 \]

Step 3: Identify electrons with \( l = 2 \) (d-orbitals).
For \( l = 2 \), electrons are in d-orbitals.
d-orbital present is:
\[ 3d^5 \]
Total electrons:
\[ 5 \]

Step 4: Conclusion.
Thus, number of electrons are:
\[ l = 1 \Rightarrow 12,\quad l = 2 \Rightarrow 5 \]
Therefore:
\[ \boxed{12 \text{ and } 5} \]