Questions: Which nuclear equation is an example of positron emission?
Multiple Choice
- 87^221 Fr → 85^217 At+
- 13^27 Al + 2^4 He → 15^30 O
- 8^15 O → 7^15 N+
- 62^235 U + On → 52^13 Te + 40^7 Zr
- 93^239 Np → 94^239 Pu
Transcript text: Which nuclear equation is an example of positron emission?
Multiple Choice
${ }_{87}^{221} \mathrm{Fr} \rightarrow{ }_{85}^{217} \mathrm{At}+$
${ }_{13}^{27} \mathrm{Al}+{ }_{2}^{4} \mathrm{He} \rightarrow{ }_{15}^{30} \mathrm{O}$
${ }_{8}^{15} \mathrm{O} \rightarrow{ }_{7}^{15} \mathrm{~N}+$
${ }_{62}^{235} \mathrm{U}+\mathrm{O}_{\mathrm{n}} \rightarrow{ }_{52}^{13} \mathrm{Te}+{ }_{40}^{7} \mathrm{Zr}$
${ }_{93}^{239} \mathrm{~Np} \rightarrow{ }_{94}^{239} \mathrm{Pu}$
Solution
Solution Steps
Step 1: Identify Positron Emission
Positron emission is a type of beta decay where a proton in the nucleus is converted into a neutron, releasing a positron (\( \beta^+ \)) and a neutrino. The general form of the equation is:
\[ {}_{Z}^{A}X \rightarrow {}_{Z-1}^{A}Y + \beta^+ \]
Step 2: Analyze Each Option
Option 1:
\[ {}_{87}^{221} \mathrm{Fr} \rightarrow {}_{85}^{217} \mathrm{At} + \]
This equation represents alpha decay, not positron emission, as the atomic number decreases by 2 and mass number by 4.
Option 2:
\[ {}_{13}^{27} \mathrm{Al} + {}_{2}^{4} \mathrm{He} \rightarrow {}_{15}^{30} \mathrm{O} \]
This is a nuclear reaction involving the fusion of aluminum and helium, not positron emission.
Option 3:
\[ {}_{8}^{15} \mathrm{O} \rightarrow {}_{7}^{15} \mathrm{N} + \lambda^{0} \]
This equation shows a decrease in atomic number by 1, which is characteristic of positron emission.
Option 4:
\[ {}_{62}^{235} \mathrm{U} + \mathrm{O}_{\mathrm{n}} \rightarrow {}_{52}^{13} \mathrm{Te} + {}_{40}^{7} \mathrm{Zr} \lambda^{9} \]
This is a complex nuclear reaction, not positron emission.
Option 5:
\[ {}_{93}^{239} \mathrm{Np} \rightarrow {}_{94}^{239} \mathrm{Pu} \]
This represents beta decay where a neutron is converted into a proton, not positron emission.
Step 3: Conclusion
The correct example of positron emission is:
\[ {}_{8}^{15} \mathrm{O} \rightarrow {}_{7}^{15} \mathrm{N} + \beta^+ \]
This matches the characteristics of positron emission, where the atomic number decreases by 1.