Avogardro's number / Representative particles

[tigerwoods99]

Homework Statement

Which of the following is a representative particle?
a. cation Incorrect
b. all of these particles Correct
c. anion Incorrect
d. atom Incorrect

Homework Equations

The Attempt at a Solution

I am trying to understand why all of these are representative particles. My book says, "The term representative particle refers to the species present in a substance: usually atoms, molecules, or formula units."

I selected atom, but as you can see, that was apparently incorrect. I am just trying to understand why.

Thanks!

 

[Mark44]

Look up the definitions of cation and anion in your book.