What is the difference between a positively and negatively charged atom and how does it occur?

Answer 1

The difference is how many protons and electrons. Protons are positive, (both "p's" easier to remember) so if there are more electrons it's negative, less electrons it's positive.

When atoms have electrons added or subtracted it changes the charge, then they are known as ions. The atomic number is how many protons there are, this never changes, if it does there is a different element.

Answer 2

A positively charged atom has lost electrons, resulting in more protons than electrons. A negatively charged atom has gained electrons, resulting in more electrons than protons. This charge difference occurs when atoms interact with other atoms, gaining or losing electrons to achieve a more stable electron configuration through the formation of ions.