The Atomic Structure in the Periodic Table


Atomic structure is the positively charged nucleus and the negatively charged electrons circling around it, within an atom.

The atom itself is the fundamental building block of all matter in the universe. From cars to cats and airplanes, everything is made up of atoms.

The atom is made up of three core components which are called subatomic particles (sub meaning they are smaller than the atom itself): The neutron, proton, and electron. All of these contribute to the mass and properties of the atom.

In the centre is the nucleus. This is an area of the atom that contains the protons (positive subatomic particles) and the neutrons (neutral subatomic particles). Overall the nucleus has a positive charge due to the presence of the proton, it also contains most of the mass of the atom as the proton and neutron both have a mass of one. Expanding on this, considering 1kg is 1000g, a proton has a mass of 1.672622x10-27 Kg that is 0.0(26 0’s)1672622kg and a neutron has a mass 1.674927x10-27 Kg meaning a neutron is slightly heavier than a proton. To keep things simple we say that the mass of a proton and neutron is 1.

The atom contains 3 particles that give it identity. The nucleus contains two particles, one is the proton. The proton is a positively charged particle with a mass of one. The other particle is the neutron. The neutron is a neutrally charged particle with no charge, it has a charge of 0 unlike the proton which has a charge of +1. The proton and neutron both have a mass of 1. As you add more protons to the nucleus this changes the identity of the element meaning each atom has a different number of protons. When the number of neutrons is changed this can change the mass too but it does not change the identity. For example an element with 3 protons would be Lithium, an element with 4 protons would be Beryllium. However, if we had two atoms both with 3 protons but they had different neutrons they would be the same element but described as isotopes.

Whilst the nucleus is made of protons and neutrons due to the positive charge on the proton and neutrons having no charge this means the nucleus overall is positively charged. In the diagram, there are particles outside of the atom beyond the nucleus. These are electrons, negatively charged particles that orbit the nucleus. As electrons are negatively charged there is an attraction to the nucleus but instead of combining they orbit the nucleus, much like the planets of the solar system orbit the sun. Whilst inside the nucleus the proton and neutron are held together by a strong nuclear force, this is like a very strong glue that keeps protons and neutrons stuck together. The force between protons and electrons is the electromagnetic attraction, as they have opposite charges that attract each other. This force is not as strong as the strong nuclear force and as a result electrons can be added and removed from the nucleus. Electrons and their movement play a large part in how atoms bond together through covalent, ionic or metallic bonding and also their reactivity.  Electrons are closely linked to the number of protons. In an element the number of protons is equal to the number of electrons and they balance out each others charges. For example Lithium contains 3 protons and has 3 electrons orbiting the nucleus in shells. This means the nucleus has a 3+ charge and the electrons contribute a -3 charge. The 3+ charge of the nucleus and the -3 charge of the 3 electrons cancel out to give an overall charge of 0 meaning the element is neutral.

Terms in section

An atom is the smallest particle that makes up all matter


Matter is a term used to describe when all atoms are combined to make up large structures.


The nucleus is the term given to the centre of the atom comprising of the proton and neutron


A proton is a positive particle that makes up the atom in the nucleus with a positive charge


A neutron is a neutral sub atomic particle that makes up the nucleus with the proton


The electron is the smallest sub atomic particle that make up the atom. Has a negative charge and is located in shells that orbit the nucleus


The Origins of the Periodic Table


Understanding Element Names and Symbols