Question

Which of the following pairs have nearly same mass?
1. electron and $\beta$ particle
2. neutron and $\beta$ particle
3. proton and ${}_1^2{\text{H}}^{+}$ ion
4. $\alpha$ - particle and $H{e}^{2+}$ ion
5. proton and ${}_1^1{\text{H}}^{+}$ ion

• A. (1), (4), (5)
• B. (2), (3), (5)
• C. (2), (4), (5)
• D. (1), (3), (5)

Answer 1

The correct option is A (1), (4), (5)

1. Mass of electron = $9.1094\times {10}^{-28}$ and mass of $\beta$ particle = $9.10938188\times {10}^{-31}$ which is almost the same.
2. Mass of neutron = $1.6740\times {10}^{-24}$ and mass of $\beta$ particle = $9.10938188\times {10}^{-31}$ which is not equal.
3. Mass of proton = $1.6726\times {10}^{-24}$ and mass of ${}^{2_1}{\text{H}}^{+}$ ion = $3.343583719\times {10}^{-27}$ which is not equal.
4. Mass of $\alpha$ - particle = $6.64424\times {10}^{-27}$ and mass of $H{e}^{2+}$ ion = $6.64648\times {10}^{-27}$ which is almost equal.
5. Mass of proton = $1.6726\times {10}^{-24}$ and mass of ${}^{1_1}{\text{H}}^{+}$ ion = $1.6726\times {10}^{-27}$ which is almost