What Are Elements?
If we put these different kinds of atoms together in different ways, we can make ALL the substances in the world. Normally the atoms are all mixed up like to make substances like sand or a brick. But sometimes a substance is made of just one kind of atom, like a lump of gold. Or we can separate the different atoms so they make substances of just one kind. A substance made of just one kind of atom is called an element.
AN ELEMENT IS A SUBSTANCE MADE OF ONLY ONE KIND OF ATOM.
The element gold is made of only gold atoms.
An atom is named after its element
People knew about gold, iron and water before they knew that they were made of atoms. When they discovered that gold was made of only one kind of atom, they named them “gold atoms”, not surprisingly. What would you call the atoms that make iron? Iron atoms!
But you can’t tell from looking at a substance whether it’s made of one or more kinds of atoms, because the atoms are way too small to see. Scientists now know how to pull atoms apart, so if something is made of more than one kind they can separate it into its elements. For example, if we pass electricity through water we get hydrogen and oxygen atoms. Because we can’t separate hydrogen or oxygen any further, we know that they must then be made of only one kind of atom- they’re elements.
Elements vs Compounds
Scientists call water a compound, because it’s made of two kinds of atoms in a definite ratio. This means that if we can pull the atoms in water apart, we can make two simpler substances, hydrogen and oxygen, which are both elements. We will look at that more later.
If gold is made of gold atoms, is water made of “water atoms”? This can’t be. You might know that water is H2O, which means that it is made of both hydrogen and oxygen atoms. We will get into that more soon. This means that there can’t be a such as thing as a single “water atom”. Only elements can have the same name as the atoms that make them, as they are made of only that kind.
The classical elements
Ancient thinkers once thought that the world was made of a combination of 4 or 5 elements of nature- air, water, earth, fire and aether. They called these “elements” because they thought that they were the basic building blocks of the universe, and that everything was made of some combination of them. But we now know that everything is physically made of some combination of atoms: air is made of a combination of nitrogen and oxygen atoms, water is made of hydrogen and oxygen atoms, earth is made of many different kinds of atoms and fire is the light and heat from burning and not made of atoms at all. Although these things are not elements in the scientific sense, they are still “elements” from a traditional point of view. It just depends on the context.