Question

Correct set of four quantum numbers for the valence electron of strontium (Z = 38) is

• A. \( 5, 0, 0, +\frac{1}{2} \)
• B. \( 5, 1, 0, +\frac{1}{2} \)
• C. \( 5, 1, 1, +\frac{1}{2} \)
• D. \( 6, 0, 0, +\frac{1}{2} \)

Hint:

For valence electrons, check the highest n value and identify the corresponding l, m\(_l\), and m\(_s\) values based on orbital type.

Answer 1

The Correct Option is A

The electron configuration of Strontium (Z = 38) is: \[ 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 \] - The valence electrons are in the 5s orbital.
- The principal quantum number (\( n \)) is 5.
- The azimuthal quantum number (\( l \)) for an s-orbital is 0.
- The magnetic quantum number (\( m_l \)) is 0 (since \( m_l \) values range from \( -l \) to \( +l \)).
- The spin quantum number (\( m_s \)) is \( +\frac{1}{2} \) or \( -\frac{1}{2} \), typically chosen as \( +\frac{1}{2} \) for an unpaired electron in standard notation).
Thus, the correct set of quantum numbers is: \[ (5, 0, 0, +\frac{1}{2}) \]