Which pf the following orbitals are not possible?
`2d,4f,4g` and `6d`

Answer

To determine which of the given orbitals are not possible, we need to analyze each orbital based on the quantum numbers associated with them. The orbitals in question are: 2d, 4f, 4g, and 6d.

### Step-by-Step Solution:

1. **Understanding Quantum Numbers**:
- The principal quantum number (n) indicates the energy level or shell.
- The azimuthal quantum number (l) determines the subshell and can take values from 0 to (n-1).
- Each subshell corresponds to a specific value of l:
- s (l = 0)
- p (l = 1)
- d (l = 2)
- f (l = 3)
- g (l = 4)

2. **Analyzing 2d Orbital**:
- For n = 2, the possible values of l are 0 and 1 (i.e., s and p subshells).
- Since d corresponds to l = 2, and l cannot be 2 when n = 2, the 2d orbital is **not possible**.

3. **Analyzing 4f Orbital**:
- For n = 4, the possible values of l are 0, 1, 2, and 3 (i.e., s, p, d, and f subshells).
- Since f corresponds to l = 3, the 4f orbital is **possible**.

4. **Analyzing 4g Orbital**:
- For n = 4, the possible values of l are still 0, 1, 2, and 3.
- Since g corresponds to l = 4, and l cannot be 4 when n = 4, the 4g orbital is **not possible**.

5. **Analyzing 6d Orbital**:
- For n = 6, the possible values of l are 0, 1, 2, 3, 4, and 5.
- Since d corresponds to l = 2, and 2 is within the range of possible values for l when n = 6, the 6d orbital is **possible**.

### Conclusion:
The orbitals that are not possible are **2d and 4g**. The orbitals that are possible are **4f and 6d**.

### Final Answer:
- Not Possible: **2d, 4g**
- Possible: **4f, 6d**