An alpha particle consists of two protons and two neutrons. This composition is identical to the nucleus of a helium-4 atom.
1. Let's examine each option:
- Option A: [tex]${ }_{-1}^0 e$[/tex]
- This symbol represents an electron, specifically a beta-minus particle (β⁻), which has a charge of -1 and a negligible mass (compared to protons and neutrons).
- Option B: [tex]${ }_2^4 He$[/tex]
- This symbol represents a helium nucleus with 2 protons and 2 neutrons, which is exactly what makes up an alpha particle.
- Option C: [tex]$\beta$[/tex]
- This symbol generally represents a beta particle, which could be a beta-minus (electron) or beta-plus (positron) particle.
- Option D: [tex]$\gamma$[/tex]
- This symbol represents a gamma ray, which is a high-energy photon with no charge and no mass.
2. Comparing these options:
- An alpha particle is not an electron (Option A), nor a beta particle (Option C), nor a gamma ray (Option D).
- An alpha particle is indeed identical to a helium-4 nucleus, which matches Option B: [tex]${ }_2^4 He$[/tex].
3. Therefore, an alpha particle is best represented by Option B: [tex]${ }_2^4 He$[/tex].
