Elements

Elements are the basic chemical building blocks of matter, and atoms are the basic unit of an element. You could build living things from a handful of elements based on carbon, and you could make the water that covers most of our planet from just two elements - hydrogen and oxygen.

But to make everything on Earth you would need about 100 elements in total. Most elements occur naturally - they are locked in rocks or drifting around in the atmosphere. But since elements are made from protons, neutrons, and electrons glued together by strong forces, it's also possible to build brand new ones. Scientists have done just this in laboratories, pushing the total number of known elements to 118.

The Periodic Table

If we sort the elements into a grid according to their atomic structure, patterns emerge. Elements that behave in similar ways group together, so we can predict how an element will behave from its place in the grid. This idea is called the Periodic Table, and it was created by a Russian chemist called Dmitri Mendeleev in 1869.

Growing Atoms

Atoms get bigger and heavier as we move down each column (group) of the table. This is because there are more protons in the nucleus and more electrons in the shells (rings) around it. A shell is added each time we move another step down a group.

Shrinking Atoms

As we move along each row (period) of the table, atoms gain more protons and electrons. Each atom has the same number of electron shells, but there are more positively charged protons pulling the shells inward. This shrinks the atom, and makes it more tightly packed.

Transuranic Elements

Elements with a greater number than uranium (92) are called transuranic. Unlike elements 1-92, these aren't found in nature and have to be created in particle accelerators or nuclear reactors, which makes them very expensive to use.

What is an element?

The elements are different substances (solids, liquids, and gases) made from atoms that have different inner structures. If two atoms have the same number of protons, they are atoms of the same element. An atom is the smallest amount of an element you can have.

Atomic number

This is the number of protons inside the nucleus of the atom.

Atomic mass

This is the total number of protons and neutrons in an atom.