It is known that a neutron exists in a light atomic nucleus Which of the following also exists in the nucleus?

Analysis of the Question

The question asks for the fundamental subatomic particles that constitute the nucleus of a light atom. You are given that a neutron is present and need to identify the other particle that completes the composition of the nucleus.

Concept Explanation

According to the Rutherford-Bohr model of the atom:

1. The Nucleus: This is the dense central core of an atom. It is composed of two primary types of nucleons: protons and neutrons.
2. Protons: These are positively charged particles found inside the nucleus. The number of protons determines the atomic number of the element.
3. Neutrons: These are neutral particles (no charge) also found inside the nucleus.
4. Electrons: These are negatively charged particles that orbit the nucleus in specific energy levels or shells. They are not part of the nucleus.

While $\beta$-particles (beta particles) are high-energy electrons emitted during radioactive decay, they are not permanent structural components of a stable atomic nucleus.

Step-by-Step Solution

1. Identify the components: We know the nucleus contains nucleons. The two types of nucleons are protons and neutrons.
2. Evaluate the options: • A (An electron): Incorrect. Electrons exist in shells outside the nucleus. • B & C ($\beta$-particle): Incorrect. These are emitted during decay; they are not standard building blocks of the nucleus. • D (Proton): Correct. Protons and neutrons are the two particles that make up the nucleus of every atom (except for the simplest isotope of Hydrogen, which has only one proton).

Conclusion

The nucleus of an atom is composed of protons and neutrons. Since the question states that a neutron is present, the other particle that must be present is the proton.

Exam Tip

Remember the mnemonic "P-N" for the nucleus: Protons and Neutrons. If you ever get confused about where electrons are, remember they are the "orbiters" on the outside, while the heavy lifting (the mass of the atom) happens inside the nucleus with the protons and neutrons.