Question

Identify the nuclide produced when plutonium-239 decays by alpha emission: 239 94pu→42he + ? express your answer as an isotope using prescripts. 235 92u submithintsmy answersgive upreview part incorrect; try again; 4 attempts remaining part b identify the nuclide produced when thorium-234 decays by beta emission: 234 90th→ 0−1e + ? express your answer as an isotope using prescripts. submithintsmy answersgive upreview part part c identify the nuclide produced when fluorine-18 decays by positron emission: 18 9f→01e + ? express your answer as an isotope using prescripts. submithintsmy answersgive upreview part part d identify the nuclide produced when thallium-201 decays by electron capture: 201 81tl+ 0−1e→00γ + ? express your answer as an isotope using prescripts.

Answer 1

1. Answer is ₉₂²³⁵U

Since this is an alpha emission the atomic number of the daughter nucleus decreases by 2 while mass number decreases by 4 compared to parent atom. Since parent atom has 94 as atomic number the daughter atom should have 94 - 2 = 92 as atomic number and 239 - 4 = 235 as mass number. 

₉₄²³⁹Pu → ₂⁴He + ₉₂²³⁵U

2. Answer is ₉₁²³⁴Pa

Since this is a beta emission, a neutron is converted into a proton while emitting an electron. Hence atomic number increases by 1 compared to mass number but mass number remains as same. Hence, the atomic number of the daughter atom should be 90 + 1 = 91 which belongs to Pa. But the mass number is same as 234.

₉₀²³⁴Th → ₋₁⁰e + ₉₁²³⁴Pa

3. Answer is ₈¹⁸O

Since this is a positron emission, a proton is converted into a neutron while emitting an positron. Hence atomic number decreases by 1 compared to mass number but mass number remains as same. Hence, the atomic number of the daughter atom should be 9- 1 = 8 which belong to O. But the mass number is same as 18.

₉¹⁸F → ₊₁⁰e + ₈¹⁸O

4. Answer is ₈₀²⁰¹Hg

This is an electron capture decay. A proton is converted into a neutron by emitting a gamma ray. In this process mass number remains as same as parent atom which is 201, but the atomic number is decreased by 1 than parent atom. Hence atomic number of daughter nucleus is 81 -1 = 80 which belongs to Hg.

₈₁²⁰¹Tl +  ₋₁⁰e →  ₀⁰γ + ₈₀²⁰¹Hg