Arrange the following particles according to their charge/mass ratio in decreasing order.
A. proton
B. α-particle
C. electron
D. tritium atom after losing the single electron
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → C, A, B, D
Compare the specific charge q/m, taking the proton mass \( m_p \) as the unit of mass (the neutron mass is nearly the same) and e as the unit of charge. The electron mass is about \( m_p/1836 \), and a tritium atom that has lost its only electron is a triton: one proton and two neutrons.
\( \text{(C) electron: } q/m \approx 1836\,e/m_p \)
\( \text{(A) proton: } q/m = e/m_p \)
\( \text{(B) } \alpha\text{-particle: } q/m = 2e/4m_p = 0.5\,e/m_p \)
\( \text{(D) triton: } q/m = e/3m_p \approx 0.33\,e/m_p \)
So the decreasing order is (C), (A), (B), (D).