Let's carefully examine the given details:
1. Definition of an Alpha Particle:
An alpha particle is described as having 2 protons, 2 neutrons, and 0 electrons. This particle is essentially the nucleus of a helium-4 atom without any electrons.
2. Atomic Composition:
- Protons determine the atomic number of an element.
- Combining the protons and neutrons gives the mass number of the element.
3. Isotope Clarification:
- Lithium-7:
- Atomic Number: 3 (3 protons)
- Number of Neutrons: 4
- Total Mass: 7 (3 protons + 4 neutrons)
- Helium-4:
- Atomic Number: 2 (2 protons)
- Number of Neutrons: 2
- Total Mass: 4 (2 protons + 2 neutrons)
- Hydrogen-2 (Deuterium):
- Atomic Number: 1 (1 proton)
- Number of Neutrons: 1
- Total Mass: 2 (1 proton + 1 neutron)
- Helium-2:
- Atomic Number: 2 (2 protons)
- Number of Neutrons: 0
- Total Mass: 2 (2 protons + 0 neutrons)
Given the above clarifications, an alpha particle fits the description of an isotope with 2 protons and 2 neutrons.
Conclusion:
Among the options provided, the only isotope that matches the description of having 2 protons and 2 neutrons is helium-4.
Therefore, the correct answer is:
Helium-4
