What Are Atoms?

A beach is made of sand grains
Our world is made of thousands of different substances- wood, metal, plastic, glass etc.  But what are they made of?  Imagine that you look at a beach from far away.  It looks like one big smooth thing.  But we know that, up close, a beach is made of trillions of little sand grains.  We can say that sand grains are the building blocks of the beach.

There are other examples of a big thing being made of lots of little things put together.  How about a brick building?  Bricks are the building blocks of the building.  What are other examples?  How about a swarm of bees, or a forest of trees?  Did you know that a cloud is made of trillions of little liquid water droplets?

But what is a sand grain made of? 
To see a sand grain’s building blocks, we need to magnify it using a powerful electron tunnelling microscope.   This can make the sand grain look a billion times bigger, and when we look through the microscope we see that a sand grain is made of two kinds of little round particles.  These are called atoms– the red ones are oxygen atoms, and the grey ones are silicon atoms. (Actually, atoms aren’t really coloured, but we show them like this to tell them apart more easily.)

The atoms are too small to see with our eyes, so when you look at a sand grain, you only see a single thing, a collection of atoms.

A sand grain is made of 2 kinds of atoms- oxygen and silicon.

The word ‘atom’ comes from the ancient Greek word meaning ‘uncuttable’ or ‘indivisible’.  If you could cut a sand grain in half, over and over many times, you would eventually be unable to cut it any further because you will reach the size of its smallest particle, a single atom.

What is a brick made of?
A brick is the building block of a building, but what is a brick made of?  If we magnify a brick, we can see that it’s made of aluminium and oxygen atoms too, but there are some extra ones as well- hydrogen, calcium and iron.  The properties of the substance- its colour, hardness, melting temperature etc- depend on what atoms it’s made of, as well as the way they are arranged.

And if we looked at a banana, toothpaste, or a marble, we would find that they are all made of atoms too.   It turns out that atoms are the basic building blocks of ALL objects.

Atoms are the basic building blocks of matter.

A brick is made of many kinds of atoms

The whole world is made of 92 kinds of atoms

If we magnified ALL the substances in the world, we would find 92 different kinds of atoms.  It took scientists thousands of years to discover all of these, which is not surprising because they are so small.  They have been hiding in plain sight.  A human hair is about 1 millimeter in diameter, yet is about 1 million atoms wide.  If we can just see a hair, what chance have we got of seeing an atom with our eyes?  None.

You’ve probably heard of many of the different kinds of atoms- hydrogen, helium, lithium, carbon, nitrogen, oxygen, aluminium, silicon, sulfur, copper, iron, silver and gold.  But there are some you probably haven’t heard of, like niobium or rhonium.

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