# What are the particles with the smallest relative mass that moves around the nucleus?

You are looking for $\text{electrons}$ but I really think you should read a text.
Electrons are conceived to whizz about a massive nuclear core, and $\text{mass"_"electron} = 9.11 \times {10}^{-} 31 \cdot k g$. The protonic mass is $1.67 \times {10}^{-} 27 \cdot k g$...i.e. 4 orders of magnitude more massive.