Atoms and molecules, What are atoms and molecules?

Atoms and molecules

What are atoms and molecules?

All  the matter in the universe that we know of is made of tiny, invisible particles called atoms. Atoms are crammed into everything you can see - from the skin on your fingers to the words in this book - and things you can't see too, such as the air you breathe and the cells rushing through your blood. 

The idea of atoms is one of the oldest in science. Some Ancient Greek Philosophers thought atoms were the smallest possible bits of matter and couldn't be broken down further. They chose the name atom because it means "uncuttable" or "indivisible". This early concept of atoms lived on for thousands of years, until, in the early 20th century, ingenious scientists "split the atom", smashing it apart into even tinier particles.

When atoms combine, they make bigger clumps called molecules. Although there are only. 100 types of atom, together they can form millions of different types of molecules.

The structure of an atom

Inside an atom are even tinier particles of matter called protons, neutrons and electrons. Protons and electrons are are found in the centre of an atom,which is called nucleus, and are locked tightly together by powerful forces. Electrons spin up, down, and around outside the nucleus within areas called electron shells.

The nucleus

A cluster of protons and neutrons make up the nucleus of an atom. It makes up most of an atom's weight, but only takes up a tiny amount of it's volume. Outside the nucleus, more than 99.99 per central of an atom is just empty space. If an atom were the size of a football stadium, the nucleus would be the size of a pea in the centre of it , and the electrons would be zooming around the outer stands .

Proton 

Protons have a positive electric, charge and are   attracted to electrons.

 Neutron 

These are around same size as protons. Neutrons are neutrals, which means they don't have an electric charge and aren't attracted to electrons or protons.

Electron shells

An atom usually has an equal number of negatively charged electrons and positively charged protons. Some big atoms have more than 100 of both. The carbon atom shown here has six of each. Electrons are arranged in layers ( called electron shells) around nucleus,like satellites around a planet. Bigger atom have more shells than smaller ones. Imagining electrons in shells helps us to understand how atoms join together to form molecules.

Electron

These particles are about 2,000 times lighter than protons and neutrons and orbit the nucleus at almost the speed of light. They have a negative electric charge.

Making molecules

Atoms can join together - or bond-to make molecules. A molecule can be made of the same atoms or  different ones. Gases such as hydrogen have simple molecules made of just two atoms, while plastics can be made from endlessly repeating molecules made up of thousands of atoms joind together in very long lines. 

Water (H2O)

A molecule of water is made from two hydrogen atoms joined to one oxygen atom.

Carbon dioxide (CO2)

A carbon dioxide molecule is made from two atoms of oxygen joined to one atom of carbon.

How atoms Bond

Atoms bind together to make molecules using their electrons,which they give, take or share with each other. Three main types of Bond hold atoms together.

Ionic bond

One atoms gives electrons to another. The first atom becomes positively charged and the second atom becomes negatively charged, so the atoms attract and lock.

Covalent bond

Two atoms share their out electrons by making their outer electron shells or overlap.

Metallic bond

Metals Bond into What's called a crystal lattice by sharing their outer electrons in a giant cloud.

Quarks and strings

Is a string smaller than a quark?

If the nucleus of an atom is built from protons and neutrons, what are these thing made of? It seems that each consists of three even smaller particles called quarks. Some scientists believe that everything is really made from vibrations of matter or energy called strings. But so far no one knows what, if anything, strings are made of.