Understanding the Charge of an α Particle

An α particle is a specific type of particle emitted during some forms of radioactive decay. It is fundamental to understanding nuclear physics and radiation.

Let's analyse the options provided regarding the charge of an α particle:

• negative charged particle
• positively charged particle
• neutral particle
• massless positively charged particle

To determine the correct charge of an α particle, we need to know its composition.

Composition of an α Particle

An α particle is identical to the nucleus of a helium atom. It consists of:

• 2 protons
• 2 neutrons

The symbol for an alpha particle can be represented as $_2^4\text{He}^{2+}$ or simply $\alpha$.

Determining the Charge

Now let's consider the charges of its components:

• Each proton carries a charge of $+1e$ (where $e$ is the elementary charge).
• Each neutron is electrically neutral, meaning it has a charge of $0$.

The total charge of the α particle is the sum of the charges of its constituent particles:

Total charge = (Number of protons × Charge of a proton) + (Number of neutrons × Charge of a neutron)

Total charge = $(2 \times +1e) + (2 \times 0)$

Total charge = $+2e + 0$

Total charge = $+2e$

Since the elementary charge $e$ is positive, the total charge of an α particle is positive. Specifically, it carries a charge of $+2e$. This makes the α particle a positively charged particle.

Evaluating the Options

• negative charged particle: Incorrect, as shown by the composition, the charge is positive.
• positively charged particle: Correct, the calculation shows a total charge of $+2e$.
• neutral particle: Incorrect, it has a net positive charge. Neutral particles like neutrons or gamma rays have no charge.
• massless positively charged particle: Incorrect. An α particle has significant mass, approximately 4 atomic mass units (amu), which is the combined mass of 2 protons and 2 neutrons. Particles like photons are massless, but an α particle is not.

Therefore, an α particle is a positively charged particle, identical to a helium nucleus, and is commonly involved in alpha radiation during radioactive decay processes.

Understanding the nature and charge of an α particle is crucial in studying nuclear reactions and the effects of radiation.