According to the modern atomic theory, most of an atom is empty space. An atom consists of a small, dense nucleus surrounded by electrons. Atoms contain three types of subatomic particles: protons, neutrons and electrons. The nucleus contains only protons and neutrons.

• Protons are particles with a positive charge.
• Neutrons are particles with a neutral, or no, charge.
• Electrons are particles that orbit around the nucleus in regions with different levels of energy. Electrons are much smaller in size and mass than protons and neutrons and have a negative charge.

Let's Build an Atom!

1. Start by clicking on the interactive "Atom"
2. You can add protons, neutrons, and electrons.

With the addition of which particle do you notice the element name change?

Do you remember what value this refers to on the Periodic Table?

3. Click on the green + to expand the "Net Charges"

When does the atom to become an ion?

4. Click the green + to expand the "mass" section.

The addition of which particle will not change the mass?

5. Have more trivia fun: Click on any Game to test your atomic structure knowledge!