ELI5: What is an atom?

Imagine you have a LEGO brick. Now, imagine you break that LEGO brick into smaller and smaller pieces. Eventually, you'll get to the smallest possible piece that still is LEGO. That's kind of like an atom.

An atom is the smallest piece of something (like a LEGO brick) that still is that something. Everything around you – your toys, your food, even you – is made of tiny, tiny atoms.

Think of it this way:

• Everything is made of matter.
• Matter is made of tiny pieces called molecules.
• Molecules are made of even tinier pieces called atoms.

Inside the atom, there are even smaller parts:

• Protons: These have a positive (+) charge.
• Neutrons: These have no charge (they're neutral).
• Electrons: These have a negative (-) charge and whiz around the protons and neutrons.

Different kinds of atoms are called elements. For example, hydrogen and oxygen are elements. Water (H2O) is a molecule made of two hydrogen atoms and one oxygen atom stuck together.

So, an atom is the smallest piece of an element that still has all the properties of that element. It's like the fundamental LEGO brick of everything!