How many electron in K (Z =19) have n = 2, l = 1 ?

Options

A. 2
B. 4
C. 6
D. 8

Explanation

To determine how many electrons in potassium (K, atomic number Z = 19) have the quantum numbers n = 2 and l = 1, we can follow these steps:

### Step 1: Understand the Quantum Numbers
- The principal quantum number (n) indicates the energy level of the electron. Here, n = 2 means we are looking at electrons in the second energy level.
- The azimuthal quantum number (l) indicates the shape of the orbital. For l = 1, this corresponds to the p orbital.

### Step 2: Write the Electron Configuration of Potassium
- The atomic number of potassium is 19, which means it has 19 electrons. The electron configuration can be written as:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

### Step 3: Identify Electrons in the n = 2 Level
- In the electron configuration:
- The n = 2 level consists of:
- 2s² (2 electrons)
- 2p⁶ (6 electrons)
- Therefore, the total number of electrons in the n = 2 level is 2 + 6 = 8 electrons.

### Step 4: Identify Electrons in the l = 1 Sublevel
- Since l = 1 corresponds to the p orbital, we focus on the 2p sublevel.
- From the configuration, we see that the 2p sublevel has 6 electrons.

### Conclusion
- The number of electrons in potassium that have n = 2 and l = 1 (which corresponds to the 2p orbital) is **6**.

### Final Answer
The number of electrons in K (Z = 19) that have n = 2 and l = 1 is **6**.