1. Protons: Positively charged particles located in the atom's nucleus.

2. Neutrons: Neutrally charged particles also located in the nucleus.

3. Electrons: Negatively charged particles that orbit the nucleus in a cloud-like region called the electron cloud.

Here's a breakdown of their roles:

* Protons determine the element. The number of protons in an atom's nucleus defines what element it is. For example, all carbon atoms have 6 protons.

* Neutrons contribute to the atom's mass and can vary within an element. This variation leads to isotopes, atoms of the same element with different numbers of neutrons.

* Electrons are responsible for chemical bonding and interactions between atoms. They occupy specific energy levels or shells around the nucleus.

It's important to note that atoms are mostly empty space. The nucleus is incredibly tiny compared to the size of the electron cloud.