7.2 describe the structure of an atom in terms of protons, neutrons and electrons and use symbols such as 14 C to describe a particular nuclei

The structure of an atom is super simple when you break it down... 

- all atoms contain a nucleus and electrons

- the nucleus of an atom is made up of protons and neutrons

- the total number of protons and neutrons is called the mass (or nucleon) number

- electrons surround the nucleus in electron shells

- the number of protons is the same as the number of electrons

- the number of protons/electrons is known as the atomic (or proton) number

From the mass number and proton number we can learn how many protons/neutrons an atom contains. For example, if an atom of carbon has a mass number of 14 and a proton number of 6, we know that there must be 6 protons in the nucleus. To find out how many neutron are in the shell, just minus the proton number from the mass number... 14 - 6 = 8, therefore there are 8 neutrons in this isotope of carbon.