The number of electrons present in the K shells of hydrogen and helium are

Options

A. 2 and 1, respectively
B. 2 in both the elements
C. 1 and 2, respectively
D. 1 in both the elements

Answer

To determine the number of electrons present in the K shells of hydrogen and helium, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Numbers**:
- The atomic number of hydrogen (H) is 1.
- The atomic number of helium (He) is 2.

2. **Understand the Relationship Between Atomic Number and Electrons**:
- For a neutral atom, the number of protons is equal to the number of electrons. Thus:
- Hydrogen has 1 electron.
- Helium has 2 electrons.

3. **Determine the Electron Configuration**:
- The K shell is the first shell around the nucleus and can hold a maximum of 2 electrons.
- For hydrogen, with 1 electron, the electron configuration is:
- K shell: 1 electron.
- For helium, with 2 electrons, the electron configuration is:
- K shell: 2 electrons.

4. **Conclusion**:
- Therefore, the number of electrons in the K shell of hydrogen is 1, and for helium, it is 2.

### Final Answer:
- The number of electrons present in the K shell of hydrogen is **1** and for helium is **2**.

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