If `n = 6`, the correct sequence for filling of electrons will be.

Options

A. ns`rarr` (n-1)d`rarr`(n-2)f`rarr`np
B. ns `rarr`(n-2)f`rarr`np`rarr`(n-1)d
C. ns`rarr`np`rarr`(n-1)d`rarr`(n-2)f
D. ns`rarr`(n-2)f`rarr`(n-1)d`rarr`np

Explanation

To determine the correct sequence for filling of electrons when \( n = 6 \), we will use the Aufbau principle, which states that electrons fill atomic orbitals in order of increasing energy levels. The order of filling is determined by the \( n + l \) rule, where \( n \) is the principal quantum number and \( l \) is the azimuthal quantum number.

### Step-by-Step Solution:

1. **Identify the Subshells for \( n = 6 \)**:
- For \( n = 6 \), the subshells that can be filled are:
- \( 6s \) (where \( l = 0 \))
- \( 6p \) (where \( l = 1 \))
- \( 5d \) (where \( l = 2 \))
- \( 4f \) (where \( l = 3 \))

2. **Calculate \( n + l \) Values**:
- For each subshell, calculate \( n + l \):
- \( 6s: n + l = 6 + 0 = 6 \)
- \( 6p: n + l = 6 + 1 = 7 \)
- \( 5d: n + l = 5 + 2 = 7 \)
- \( 4f: n + l = 4 + 3 = 7 \)

3. **Determine the Order of Filling**:
- According to the \( n + l \) rule, we fill the subshell with the lowest \( n + l \) value first. If there are ties (as with \( 6p \), \( 5d \), and \( 4f \)), we fill the subshell with the lowest \( n \) value first.
- The order based on the calculated \( n + l \) values is:
- \( 6s \) (6)
- \( 4f \) (7, lower \( n \))
- \( 5d \) (7, higher \( n \))
- \( 6p \) (7, highest \( n \))

4. **Final Sequence for Filling**:
- Therefore, the correct sequence for filling of electrons when \( n = 6 \) is:
- \( 6s \) → \( 4f \) → \( 5d \) → \( 6p \)

### Summary of the Sequence:
The correct order for filling electrons is:
- \( 6s \)
- \( 4f \)
- \( 5d \)
- \( 6p \)