Question

Consider the last electron of an element having atomic number $9$ and choose the correct option.

• A. Sum of total nodes = 1
• B. n = 2; l = 0
• C. Last electron enters in 2s subshell
• D. There are 5e^- with l = 0

Hint:

When determining the quantum numbers, consider the electron configuration and the shell the electron occupies.

Answer 1

The Correct Option is B

The element with atomic number 9 is Fluorine (F). The electron configuration of Fluorine is: \[ 1s^2 \, 2s^2 \, 2p^5 \] The last electron (9th electron) enters the \( 2p \) orbital.
- For the last electron, the quantum numbers are:
- The principal quantum number (\( n \)) = 2 (since it is in the second shell).
- The azimuthal quantum number (\( l \)) = 0 (since it is in an \( s \)-orbital).
Thus, the correct answer is (2) \( n = 2; l = 0 \).