All things around us, whether solid, liquid, or gas, are made up of tiny particles called atoms. These atoms are incredibly small that even the most powerful microscope cannot see them.

To give you an idea of how small they are, imagine this: a tiny 50-pence coin contains about 77 quintillion atoms! That's 77, followed by 18 zeros. It's hard to wrap your head around such a vast number, but it shows how tiny atoms are.

These tiny particles combine in various ways to form the objects we see around us every day, from the air we breathe to the food we eat and the clothes we all wear. Understanding atoms and their properties is essential in the study of chemistry and can help us make sense of our world.

Protons, Neutrons and Electrons

Atoms are the building blocks of matter, and they are made up of three different types of particles: protons, neutrons, and electrons. Protons and neutrons are located in the nucleus, which is at the centre of the atom, while electrons orbit around the nucleus in shells or energy levels.
Atom Structure Diagram
Atom Structure Diagram

Protons are positively charged particles, and each proton has a mass of approximately one atomic mass unit (AMU). Neutrons, on the other hand, have no electric charge but a mass similar to protons. Electrons are negatively charged particles much smaller than protons and neutrons, and they are responsible for the chemical behaviour of atoms.

The number of neutrons can vary, but atoms with the same number of protons and different numbers of neutrons are called isotopes. The number of electrons in an atom is also important, as it determines how the atom interacts with other atoms.

The size of an atom is determined by the space between the nucleus and its outermost electron shell. This distance is called the atomic radius, typically around 0.1 nanometers - or 1 x 10-10 meters for most atoms. It's important to note that the size of an atom can vary depending on the element and the number of electrons it has.

In summary, atoms contain protons, neutrons, and electrons, and the number of these particles determines the element and the atom's chemical behaviour. The atomic radius is a measure of the size of an atom, and the distance between the nucleus and the outermost shell of electrons determines it.


1. The nucleus is located at the centre of the atom.
2. The nucleus contains protons and neutrons.
3. The nucleus has a positive charge because of the protons.
4. The nucleus of the atom contains most of its mass.
5. The size of the nucleus is approximately 0.0000000000001 meters or 1 femtometer.


1. Electrons move around the nucleus in electron shells.
2. Electrons are negatively charged and very tiny; however, they cover a lot of space.
3. The volume of their orbits determines the size of the atom.
4. Electrons have almost no mass.

Number of Protons = Number of Electrons

Unlike ions, the atom is neutral because it has no charge overall. It is because they have the same number of protons as electrons.
The charge on the electrons is the same size as the charge on the protons, except that the charges are in the opposite direction, so they cancel each other out.
The number of protons in an ion does not equal the number of electrons in the ion. As a result, there is an overall charge associated with it. For example, an ion with a charge of 5 has five more electrons in its structure than protons.

Deciphering chemical symbols

An illustration of a chemical symbol can be observed below. The symbol represents the element Carbon, identified as "C". Beneath it, there is a visual aid explaining the significance of each segment.

Chemical Symbol Example: Carbon
Chemical Symbol Example: Carbon

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