Question

Which of the following quantum numbers increases down the group in the modern periodic table?

• A. Principal quantum number
• B. Azimuthal quantum number
• C. Magnetic quantum number
• D. Spin quantum number

Answer 1

The Correct Option is A

Correct answer: Principal quantum number 

Explanation:
In the Modern Periodic Table, as we move down a group, new electron shells are added to the atoms of the elements. This means the value of the principal quantum number (n) increases. 

- Principal quantum number (n): Represents the main energy level or shell. It increases with each period down the group.
- Azimuthal quantum number (l): Depends on the value of \( n \) and can vary within the same shell.
- Magnetic quantum number (m): Depends on \( l \), and does not follow a regular trend down the group.
- Spin quantum number (s): Always \( +\frac{1}{2} \) or \( -\frac{1}{2} \), so it remains constant. 
Thus, the quantum number that increases down the group is the Principal quantum number.