The model of the atom we used at GCSE is not sufficient for A level but it is really important to have an appreciation for how different models of the atom were developed, based on the experimental evidence of the time, and who the key players were. You can find a great overview on TedEd.
We also need to understand that different models serve different purposes and it is still preferable to use an older, solar system model to explain simple bonding, for example or perhaps Dalton’s very simple model to explain the geometry of a crystal. However, if we want to explain the intricacies of emission spectroscopy, we will need to turn to Bohr and Schrödinger.
Developing a classical model of the atom
We are all familiar with the ‘solar system’ model of the atom that we used at GCSE to explain the properties of elements and compounds and their reactions (very successfully) – but where did it come from and where is the evidence?
Atomic orbitals, sub-orbitals and electron configurations
At GCSE we learnt that electrons are arranged in shells or energy levels around a central nucleus. The atom looked like the solar system and this model was perfectly sufficient to explain what we needed to understand at GSCE.
But now it it time to upgrade our working atomic model…
Wavefunctions, quantum numbers and the atomic orbital
Wavefunctions and quantum numbers are the foundations of our current understanding of atomic structure, and it turns out that the electron, like all matter, has both wave and particle properties – we are very definitely working in the quantum realm now.
Atomic absorption and emission spectroscopy
How can we possibly know what elements are present in the stars? It’s not like we can nip off and get ourselves a sample …
The answer is spectroscopy – using light as an analytical technique …
Ions and ionisation energies
An ion is an atom that has gained or lost electrons so that it is now charged – losing electrons forms cations which are positively charged and gaining electrons forms anions which are negatively charged.
Nuclear fusion reactions
Have you ever wondered where the elements originally came from?