Elements are the simplest pure substances in chemistry. Every element is made of very tiny particles called atoms. An atom is the smallest unit of an element that still has all its properties. This means if you break down an element into atoms, each atom still behaves like that element.

Atoms are like building blocks. Just like bricks build a wall, atoms build everything around us. Every element, whether it’s oxygen, gold, or iron, is made up of one kind of atom. That’s why scientists say atoms are the basic units of matter.

The other choices — molecules, compounds, and H2O — are related but different. Molecules are made of two or more atoms joined together. Compounds are substances made from different elements joined together, like water (H2O), which is made of hydrogen and oxygen atoms.

So, when we ask what elements are made of, the simple answer is: atoms. Knowing this helps you understand many science topics, especially in chemistry and physics.