number of particles relative mass of particles types of particles present charges of particles present
I gave my students this multiple choice question: A teacher builds a model of a hydrogen atom. A red golf ball is used for a proton, and a green golf ball is used for an electron. Which is not accurate concerning the model?

Only one answer is correct among these 4 choices:
- number of particles
- relative mass of particles
- types of particles present
- charges of particles present

Could you tell me which one is correct?

relative mass of particles