Class 12 NEET Physics Atoms and Nuclei Part 1

Concept:Alpha particles are helium nuclei consisting of 2 protons and 2 neutrons, carrying a positive charge.Explanation:1. Composition: An alpha particle is the nucleus of a helium atom, containing 2 protons and 2 neutrons.2. Charge: Since it has 2 protons and no electrons, it carries a net positive charge of $+2e$ (where $e$ is the elementary charge).3. Nature: An alpha particle is essentially a helium nucleus that has lost its 2 electrons, making it a doubly ionized helium atom or $\mathrm{He}^{2+}$.4. Verification of options:

• A. Neutrally charged → ✗ (Alpha particles are positively charged)
• B. Positron → ✗ (A positron is the antimatter counterpart of an electron)
• C. Protons → ✗ (An alpha particle contains 2 protons + 2 neutrons, not just protons)
• D. Ionized helium atoms → ✓ (Correct: doubly ionized helium nucleus)

Answer:D. Ionized helium atomsAlpha particles are ionized helium atoms (specifically $\mathrm{He}^{2+}$ nuclei) with a charge of $+2e$.