What will be the sum of principle and azimuthal quantum number of last electron of Argon?

Answer

To solve the question about the sum of the principal and azimuthal quantum numbers of the last electron of Argon, we can follow these steps:

### Step 1: Determine the Electron Configuration of Argon
Argon (Ar) is a noble gas with an atomic number of 18. Its electron configuration is:
\[ \text{Ar: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \]

### Step 2: Identify the Last Electron
In the electron configuration of Argon, the last electron enters the 3p orbital.

### Step 3: Determine the Principal Quantum Number (n)
The principal quantum number (n) indicates the main energy level of the electron. For the last electron in the 3p orbital:
\[ n = 3 \]

### Step 4: Determine the Azimuthal Quantum Number (l)
The azimuthal quantum number (l) defines the shape of the orbital. For p orbitals:
\[ l = 1 \]
This is because:
- s orbital (l = 0)
- p orbital (l = 1)
- d orbital (l = 2)
- f orbital (l = 3)

### Step 5: Calculate the Sum of the Quantum Numbers
Now, we need to find the sum of the principal quantum number (n) and the azimuthal quantum number (l):
\[ \text{Sum} = n + l = 3 + 1 = 4 \]

### Conclusion
The sum of the principal and azimuthal quantum numbers of the last electron of Argon is:
\[ \text{Answer: } 4 \]

---