Atomic Structure: Question 6

Worked solution

Step 1: Recall the defining properties of each particle

Each sub-atomic particle is defined by its relative charge and relative mass, both measured against the proton as the reference point:

• Proton: relative charge $+1$, relative mass $1$.
• Neutron: relative charge $0$ (it is uncharged), relative mass $1$ (almost identical to the proton’s mass).
• Electron: relative charge $-1$ (opposite in sign to the proton, equal in size), relative mass $\frac{1}{1840}$, small but not zero.

Step 2: Match against option A

$\text{Proton: } +1,\ 1 \qquad \text{Neutron: } 0,\ 1 \qquad \text{Electron: } -1,\ \tfrac{1}{1840}$

This matches option A exactly.

Step 3: Why the other options are wrong

• B gives the electron a relative charge of $+1$, which would make it behave like a proton. The electron’s charge is $-1$, opposite to the proton’s.
• C gives the neutron a relative charge of $+1$, confusing it with the proton. The neutron is electrically neutral (charge $0$), which is exactly why it does not contribute to an atom’s overall charge.
• D gives the electron a relative mass of exactly $0$. Although the electron’s mass is small enough to be ignored in most calculations of atomic mass, it is not literally zero. It has a small but measurable rest mass, about $\frac{1}{1840}$ of a proton’s mass.

Final answer

• $\boxed{\text{Option A}}$: proton ($+1$, $1$), neutron ($0$, $1$), electron ($-1$, $\frac{1}{1840}$).