Which of the following symbols represents an alpha particle?

• A. He^{2+}
• B. ^{4}_{2}He
• C. e^{-}
• D. n^{0}

Answer: (B)

Verified step by step guidance

1. Understand what an alpha particle is: it is a type of ionizing radiation consisting of 2 protons and 2 neutrons, which is essentially a helium nucleus.
2. Recall that the symbol for an alpha particle is the helium nucleus with a mass number of 4 and an atomic number of 2, written as \(^{4}_{2}He\).
3. Analyze the given options: \(He^{2+}\) represents a helium ion with a +2 charge but does not explicitly show the mass number; \(e^{-}\) is an electron; \(n^{0}\) is a neutron.
4. Recognize that the correct symbol for an alpha particle must include both the mass number (4) and atomic number (2), indicating it is a helium nucleus, not just a helium ion or other particle.
5. Conclude that \(^{4}_{2}He\) correctly represents an alpha particle because it shows the helium nucleus with 2 protons and 2 neutrons.