What's an element?

2019 is the 150th birthday of the chemist's best friend, the periodic table of elements. But what exactly is an element? Jenny Gracie and Adam Murphy have the quick fire science on the subject...

Jenny - Do you remember that giant wall chart that stared at you during science class at school? Like a game of tetris - lines of different coloured blocks slotted into a grid, with a few more lines of blocks below. This chart actually shows all the building blocks, or elements, that make up everything on Earth, from the microphone I’m speaking into, to the ears that you are listening with. This special table tells scientists how these elemental building blocks behave.

Adam - But what actually is an element? Each element is made up of one type of atom, and each is given a letter, like H for hydrogen, or O for Oxygen. Atoms have 3 basic building blocks themselves - protons, neutrons and electrons. In the centre, the nucleus, you’ll find the positively charged protons and neutral neutrons. So to balance the charge, whizzing around the nucleus are layers of negatively charged electrons. What defines one element from another - is how many protons it’s got (called the atomic number). Hydrogen has 1, oxygen has 8, and you’ll see this number next to each symbol on the periodic table.

Jenny - Now the vertical columns in the table are called groups, and these can be thought of as element families. Each group has the same number of electrons in its outer layer, which tell us how it might react with other elements. The first group all have 1 outer electron, and these often react violently with water, group 2 have 2 outer electrons and the pattern pretty much continues across the table. It is these outer electrons that form bonds with other elements, and also what determines the shared properties of a group.

Adam - Some elements like iron, copper and gold have been used by ancient civilisations for thousands of years. To date, there have been 118 elements discovered. To mark it is 150th birthday, we’re taking a tour of the periodic table, asking; how we tell one element from another; are we using elements sustainability, and what might the future hold for life’s essential building blocks.