Fundamental Particles (Oxford AQA International A Level Chemistry)
Revision Note
Written by: Alexandra Brennan
Reviewed by: Stewart Hird
The Structure of an Atom
All matter is composed of atoms
Atoms 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
Protons and neutrons are sometimes referred to as nucleons because they are found in the nucleus
The nucleus has an overall positive charge
This is because 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
Our understanding of the atomic model has evolved over time as a result of evidence from various investigations and experiments
The structure of an atom
Subatomic Particles
Protons, neutrons and electrons are so small that it is not practical to measure their charges using conventional units, such as coulombs
Instead, their charges are compared to each other
This is why they are called relative electrical charges
The relative electrical charges and masses of the subatomic particles are:
Table of relative electrical charges
Sub-atomic particle | Relative electrical charge | Relative Mass |
---|---|---|
Proton | +1 | 1 |
Neutron | 0 (neutral) | 1 |
Electron | -1 |
Atoms have no overall charge
This is because they have the same number of positive protons as negative electrons
The negative charge of one electron exactly cancels out the positive charge of one proton
Ions are formed when an atom loses or gains electrons to achieve a full outer shell
If an atom loses one negative electron, it forms a positively charged 1+ ion
If an atom gains one negative electron, it forms a negatively charged 1- ion
Examiner Tips and Tricks
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.
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