In chemistry, the star of the show is the ATOM. Chemistry is simply the study of how different atoms work together to make everything. As we stated in the introduction, you can think of atoms as though they were individual letters. The total letters in any language is known as the alphabet. In chemistry, the full list of all the different atoms is called the periodic table of the elements. We will study this in detail later on.

But first, let’s take a look at the anatomy of the atom. As you can see in the figure below, all atoms — except hydrogen — have 3 parts. The electron, the neutron and the proton. The electron is a tiny ball that orbits the proton and neutron bundle like a moon around a planet. In the centre, neutrons and protons huddle together to form the nucleus of the atom.

ATOM anatomy 2Electrons have a negative charge. Protons have a positive charge. And neutrons have ZERO charge (they are neutral = neutron).

For the sake of our illustrations, we make it look as though the protons and neutrons were quite close to the electrons. But in real life, if the proton-neutron nucleus was the size of your fist, the electron would be 100 KM away!

In fact, an atom is made up of well over 99% of nothing!

Now, what makes each type of atom different from the other is the number of protons, neutrons and electrons it has. For example, the simplest atom is the hydrogen atom. As we mentioned above, it is the only atom that does not have all 3 parts. It is missing a neutron. It is made up of one proton and one electron. (Fun Fact: 75% of the known mass in the universe is made up of hydrogen!)HYDROGEN anatomy

As you can imagine, because the hydrogen atom has one part with a positive charge — the proton — and one part with a negative charge — the electron — the two opposing charges cancel out and make the hydrogen atom neutral. It carries no charge. In fact, unless otherwise stated, all atoms on the periodic table of the elements are neutral. That is because they all have the same number of electrons as protons. (We can add a negative or positive charge to an atom by adding or removing electrons from that atom. But that’s for later!)

So, you will need to remember this simple truth: for neutral atoms, the…


To illustrate this, let us look at the 2nd atom on the periodic chart of the elements, Helium:

HELIUM anatomy
As you can see, whereas hydrogen has 1 proton, the Helium atom has 2 protons. And because Hydrogen is the only atom without any neutrons, the Helium atom has to match its 2 protons with at least 2 neutrons. And as the above illustration shows, because neutral Helium has 2 protons, it must also have 2 electrons.

The very next atom on the periodic table of the elements has 3 protons and therefore 3 electrons. And so goes the rest of the periodic table of the elements. Each successive atom has one more proton then the last one. And if it is a neutral atoms, it has the same number of electrons as it does protons. Neutrons on the other hand, can vary. For example, the element after Helium is known as Lithium. With Lithium’s 3 protons and 3 electrons it has 4 neutrons. It looks like this:

LITHIUM anatomyYou may be wondering “how can I tell how many neutrons an atom has if it can have more neutrons than protons?” This will be covered in another section. But for now, remember the general rule that atoms typically have at least as many neutrons as protons.

The fourth atom on the periodic table has four protons, four electrons and five neutrons. It is called Beryllium. And as we hop one atom at a time through the whole periodic table, the number of protons and electrons grows by 1 with each hop. Boron is the next atom and it has 5 protons, 5 electrons and 6 neutrons. So on and so forth.

Before moving onto the next tutorial, we suggest you try the sample questions for this tutorial. Have fun!


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