JEE Main 2025 Apr 4 Shift 2, Chemistry Q13: Quantum Numbers

JEE Main2025Apr 4, Shift 2Chemistry

Consider the ground state of chromium atom ( $Z = 24$ ). How many electrons are with Azimuthal quantum number $l = 1$ and $l = 2$ respectively ?

Solution

Ground-state Cr configuration: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{5} 4 s^{1}$ .

$l = 1$ corresponds to $p$ orbitals. Electrons in $p$ subshells: $2 p^{6} + 3 p^{6} = 12$ .

$l = 2$ corresponds to $d$ orbitals. Electrons in $d$ subshells: $3 d^{5} = 5$ .

$∴$ 12 and 5.

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