Sub-Atomic Particles (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note
Exam code: 8465
Written by: Stewart Hird
Updated on
Relative Mass and Charge
An atom consists of a positively charged nucleus surrounded by negatively charged electrons
Protons, neutrons and electrons are the subatomic particles that make up atoms
The mass of the atom is concentrated in the positively charged nucleus which is attracted to the negatively charged electrons:
Examiner Tips and Tricks
When drawing an atom diagram, place protons and neutrons together in the central nucleus and draw electrons in shells around the outside.
The number of each particle comes from the atomic number and mass number.
Each of the subatomic particles has a different relative mass and electric charge,:
Particle | Mass | Charge |
|---|---|---|
Proton | 1 | +1 |
Neutron | 1 | 0 (neutral) |
Electron | Very small | -1 |
Atomic Number
The atomic number (or proton number) of an element is the number of protons in the nucleus of its atoms
The symbol for atomic number is Z
All atoms of a particular element have the same number of protons
Atoms of different elements have different numbers of protons
The atomic number is unique to each element and determines its position on the periodic table
Examiner Tips and Tricks
Both the atomic number and the mass number are given on the periodic table, but it can be easy to confuse them.
Think MASS = MASSIVE, as the mass number is always the bigger of the two numbers, the other smaller one is thus the atomic / proton number
Electrical Charge
Atoms have no overall electrical charge
Even though they contain charged subatomic particles, the charges cancel out
Since a proton has a charge of +1 and an electron has a charge of −1
The number of protons must equal the number of electrons for the atom to be neutral
Examiner Tips and Tricks
Protons are Positive sub-atomic particles while Neutrons are Neutral. That leaves the electrons which must therefore be negative.
Unlock more, it's free!
Join the 100,000+ Students that ❤️ Save My Exams
the (exam) results speak for themselves:
Was this revision note helpful?