Concepts Of Physics MCQ Edition [Volume 2]PhysicsThe Nucleus
Potassium-40 can decay in three modes. It can decay via ⁻ -emission, ⁺ -emission or electron capture. Determine the equations showing the end products for these three modes respectively.
Options
- A⁻: ⁴⁰₁₉ K ⁴⁰₂₀ Ca + e⁺ + ⁺: ⁴⁰₁₉ K ⁴⁰₁₈ Ar + e⁻ + Electron capture: ⁴⁰₁₉ K + e⁺ ⁴⁰₁₈ Ar +
- B⁻: ⁴⁰₁₉ K ⁴⁰₂₀ Ca + e⁻ + ⁺: ⁴⁰₁₉ K ⁴⁰₁₈ Ar + e⁺ + Electron capture: ⁴⁰₁₉ K + e⁻ ⁴⁰₁₈ Ar +
- C⁻: ⁴⁰₁₉ K ⁴⁰₁₈ Ar + e⁻ + ⁺: ⁴⁰₁₉ K ⁴⁰₂₀ Ca + e⁺ + Electron capture: ⁴⁰₁₉ K + e⁻ ⁴⁰₂₀ Ca +
- D⁻: ⁴⁰₁₉ K ⁴⁰₂₀ Ca + e⁻ + ⁺: ⁴⁰₁₉ K ⁴⁰₁₈ Ar + e⁺ + Electron capture: ⁴⁰₁₉ K + e⁻ ⁴⁰₁₈ Ar +
Correct answer
B. ⁻: ⁴⁰₁₉ K ⁴⁰₂₀ Ca + e⁻ + ⁺: ⁴⁰₁₉ K ⁴⁰₁₈ Ar + e⁺ + Electron capture: ⁴⁰₁₉ K + e⁻ ⁴⁰₁₈ Ar +
Step-by-step solution
In ⁻ decay, a neutron is converted into a proton, emitting an electron ( e⁻ ) and an antineutrino ( ). The atomic number increases by 1 . ⁴⁰₁₉ K ⁴⁰₂₀ Ca + e⁻ + In ⁺ decay, a proton is converted into a neutron, emitting a positron ( e⁺ ) and a neutrino ( ). The atomic number decreases by 1 . ⁴⁰₁₉ K ⁴⁰₁₈ Ar + e⁺ + In electron capture, an inner orbital electron is captured by the nucleus, converting a proton into a neutron and emitting a neutrino ( ). The atomic number decreases by 1 . ⁴⁰₁₉ K + e⁻ ⁴⁰₁₈ Ar +