In helium nucleus, there are.

Options

A. 2 proons and 2 elecrons
B. 2 neutrons ,12 protons and 2 electrons
C. 2 protons and 2 neutrons
D. 2 positrons and 2 protons

Explanation

To solve the question "In helium nucleus, there are," we need to analyze the structure of a helium nucleus based on its atomic notation.

### Step-by-Step Solution:

1. **Understand Atomic Notation**:
- The atomic notation for helium is written as \( ^{4}_{2}He \), where:
- \( Z \) (the atomic number) is 2, which represents the number of protons.
- \( A \) (the mass number) is 4, which is the total number of protons and neutrons.

2. **Identify the Number of Protons**:
- From the atomic number \( Z = 2 \), we conclude that there are 2 protons in a helium nucleus.

3. **Calculate the Number of Neutrons**:
- The mass number \( A = 4 \) is the sum of protons and neutrons.
- We can express this as:
\[ A = \text{Number of Protons} + \text{Number of Neutrons} \]
- Substituting the known values:
\[ 4 = 2 + \text{Number of Neutrons} \]
- Rearranging gives us:
\[ \text{Number of Neutrons} = 4 - 2 = 2 \]

4. **Conclusion about the Helium Nucleus**:
- Therefore, in a helium nucleus, there are 2 protons and 2 neutrons.

5. **Final Answer**:
- The correct answer is that the helium nucleus contains 2 protons and 2 neutrons.