Sub-Atomic Particles
- All matter is composed of atoms, which are the smallest parts of an element that can take place in chemical reactions
- Atoms are mostly made up of empty space around a very small, dense nucleus that contains protons and neutrons
- The nucleus has an overall positive charge
- The protons have a positive charge and the neutrons have a neutral charge
- Negatively charged electrons are found in orbitals in the empty space around the nucleus
The basic structure of an atom (not to scale)
- Subatomic particles are the particles an element is made up of and include protons, neutrons and electrons
- These subatomic particles are so small that it is not possible to measure their masses and charges using conventional units (such as grams and coulombs)
- Instead, their masses and charges are compared to each other using ‘relative atomic masses’ and ‘relative atomic charges’
- These are not actual charges and masses but they are charges and masses of particles relative to each other
- Protons and neutrons have a very similar mass so each is assigned a relative mass of 1 whereas electrons are 1836 times smaller than a proton and neutron
- Protons are positively charged, electrons negatively charged and neutrons are neutral
- The relative mass and charge of the subatomic particles are:
Relative Mass & Charge of Subatomic Particles Table
Examiner Tip
The relative mass of an electron is almost negligible.
The charge of a single electron is -1.602 x 10-19 coulombs whereas the charge of a proton is +1.602 x 10-19 coulombs, however, relative to each other, their charges are -1 and +1 respectively.