Neutrons can be found in all atomic nuclei except in one case. Which is this atomic nucleus and what does it consist of?

Explanation

### Step-by-Step Solution:

1. **Identify the Question**: The question asks which atomic nucleus does not contain neutrons and what it consists of.

2. **Understand Atomic Structure**: Recall that an atomic nucleus is made up of protons and neutrons. The number of protons in an atom is referred to as its atomic number, while the mass number is the sum of protons and neutrons.

3. **Examine Hydrogen Atom**: The atomic number of hydrogen (H) is 1, which means it has 1 proton. The mass number of hydrogen is also 1.

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