An element is a substance made of only one kind of atom.
When it comes to atoms, it's rare to find a substance that's made of just one kind. Normally different types of atoms are mixed in with each other somehow, like oxygen and nitrogen in air. But when we do find a substance made of just one kind of atom we call it an element. An element is made of just one kind of atom, just like our "pure" beach is made of just one kind of sand grain.
There are about 90 different kinds of atoms in the world. Usually, they are mixed together somehow, like the nitrogen and oxygen in air. But if we do find a substance made of just one kind of atom, we call it an ELEMENT. This video show us what 36 different elements are like- their colour, shininess, malleability and whether they are solid, liquid or gas.