Ever wonder why how there are so many different substances in the universe and what makes them different from each other? Why some things are heavy and others are not? Today I will be dissecting an atom and having a close look at what really inside…

Every atom has a nucleus at its core, made up of particles called protons and neutrons. This forms about 99.9% of the mass of an atom; the remaining 0.1% are electrons, which at a basic level are considered to be whizzing around the nucleus, orbiting it like the Earth orbits the Sun.

More recently, with the development in our understanding of quantum mechanics, scientists have realised that the electrons surrounding a nucleus can be more accurately considered as an electron cloud, where the electrons may be occupying any space in that cloud at any one time. The likely position of the location of the electron based on a function of probabilities can be predicted, but we do not know where exactly the electron is until we observe it. Dense areas of cloud mark areas where the electron is more likely to be, and these regions are known as electron orbitals. Theoretically speaking, the electron could be an infinite distance away from the nucleus, but the probability of this is so infinitesimally small that it can be considered to be zero. This model of the atom is less commonly used due to its complexity, so I shall not be using it today. I will, however, be writing posts on quantum mechanics in the near future, so watch this space if you’re interested.

Protons have a +1 relative charge, neutrons are (you guessed it) neutral, and electrons have a -1 relative charge. Therefore for an atom to have no charge, it needs to have the same number of protons as it does electrons; at this level, the number of neutrons in the atom is largely unimportant. This means that if we add a proton to the nucleus of an atom, an electron also needs to be added to balance out the charge.

Essentially, this is what makes every individual element different – the number of protons and electrons it contains. Oxygen for example, which most living organisms need to respire, has 8 protons in its core, and 8 electrons orbiting it. It also has 8 neutrons, which add to the total mass of the atom. The relative masses of these three sub-particles are: proton = 1, neutron = 1, electron = 1/1836 (which can be considered to be negligible). Therefore by doing some simple arithmetic we are able to deduce that an atom of the element oxygen has 16 relative atomic mass.

As more and more electrons are added to an atom, they begin to ‘fill up’ the layer in which they’re orbiting the nucleus. This means that succeeding electrons must occupy a new layer, and when that fills up, another one, and so on and so forth. These layers are known as electron shells, and it turns out that there are a set number of electrons able to occupy each shell. The first shell can hold 2 electrons only, the second can hold 8, and the third can hold 18, and so on, the general formula being 2n2, where n is the number of the electron shell. Generally we only need to focus on the electrons in the outermost shell of an atom, known as the valence shell, because they determine the chemical properties of an atom, and play a key part in the arrangement of the periodic table.

Now we understand what an atom is and what the differences are between elements. However, rarely do we see elements on their own in the world. Nearly everything you interact with on a daily basis such as water, alcohols and plastics are made up of multiple elements which have reacted with each other to form new compounds. The elements are joined together by different kinds of bonds which require energy to be broken apart. All the bonds involve electrons being either shared, exchanged or attracted.

By wielding all this fundamental knowledge on the structure of the atom, we can now venture into deeper waters and uncover more secrets about the chemical world that we live in.

Just remember, never trust atoms. They make up everything.

Harvey