How many electron in K (Z =19) have n = 4, l = 0 ?

Options

A. 1
B. 2
C. 3
D. 4

Answer

To determine how many electrons in potassium (K) with atomic number Z = 19 have the principal quantum number (n) = 4 and azimuthal quantum number (l) = 0, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number**:
Potassium has an atomic number (Z) of 19, which means it has 19 electrons.

2. **Write the Electronic Configuration**:
The electronic configuration of potassium can be written as:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

3. **Understand Quantum Numbers**:
- The principal quantum number (n) indicates the energy level of the electron. Here, n = 4.
- The azimuthal quantum number (l) indicates the shape of the orbital. For l = 0, this corresponds to an s orbital.

4. **Identify the Relevant Orbital**:
Since n = 4 and l = 0, we are looking at the 4s orbital.

5. **Count the Electrons in the 4s Orbital**:
From the electronic configuration, we see that there is 1 electron in the 4s orbital.

6. **Conclusion**:
Therefore, the number of electrons in potassium (K) with n = 4 and l = 0 is **1**.

### Final Answer:
There is **1 electron** in potassium (K) with n = 4 and l = 0.

---