For α, β⁻, β⁺ and γ, give composition, approximate rest mass and electric charge. Explain two errors in the statement: 'A beta-plus particle has zero mass because its nucleon number is zero, and gamma photons have no energy because they are massless.'

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α: helium-4 nucleus, ≈4u,+2e. β⁻: electron,9.11×10⁻³¹kg,−e. β⁺: positron,same mass,+e. γ: photon,zero rest mass,zero charge. Nucleon number is not mass; photons can carry energy despite zero rest mass. Give all four compositions and distinguish nucleus from atom. Give alpha≈4u and equal nonzero electron/positron masses. Give charges +2e,−e,+e,0 and photon zero rest mass. Explain that A counts nucleons, not kilograms. Explain that rest mass and photon energy are different concepts.

Radiation properties including antiparticles

For α, β⁻, β⁺ and γ, give composition, approximate rest mass and electric charge. Explain two errors in the statement: 'A beta-plus particle has zero mass because its nucleon number is zero, and gamma photons have no energy because they are massless.'

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