14.2.2
Atomic Model
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Atomic Model - Example
An atom has a small, positively-charged nucleus surrounded by orbiting negatively-charged electrons.
Size of Atoms vs Nucleus
Atoms have a radius of about 1 × 10-10 metres. However, the nucleus of atoms are even smaller.
Atoms
- If an atom was the size of Wembley Stadium, then...
Nucleus
- ...its nucleus would be the size of a garden pea!
The Charges and Masses of Sub-Atomic Particles
The 3 different sub-atomic particles (protons, neutrons and electrons) have different relative charges and masses. Atoms have no overall charge (are neutral). In an atom, these charges all cancel each other out.

Protons
- Protons have a relative charge of +1.
- In SI units, this is +1.60 × 10-19C.
- They are found in the nucleus.
- An element’s atomic number is the number of protons it possesses.
- All atoms of the same element have the same number of protons.
- Protons have a relative atomic mass of 1.
- In SI units, this is 1.67 × 10-27kg.

Electrons
- Electrons have a relative charge of -1.
- In SI units, this is -1.60 × 10-19C.
- They are found in fixed orbits around the nucleus.
- In any atom, the total number of negative electrons equals the number of positive protons, meaning atoms have no overall electric charge.
- Electrons have a relative atomic mass of 1/2000.
- In SI units, this is 9.11 × 10-31kg.

Neutrons
- Neutrons have a relative charge of 0 - they are neutral.
- Like protons, they are found in the nucleus.
- Neutrons have a relative atomic mass of 1 (the same as a proton).
1Physical Quantities & Units
1.1Physical Quantities & Units
2Kinematics
3Dynamics
3.1Momentum & Newton's Laws of Motion
3.2Non-Uniform Motion
3.3Linear Momentum & Conservation
4Force, Density & Pressure
4.1Force, Density & Pressure
5Work, Energy & Power
6Deformation of Solids
7Waves
7.1Simple Harmonic Motion
7.2Waves
8Superposition
9Thermal Physics
9.1Circular Motion
9.2Thermal Physics
10Communication
10.1Communication Channels
10.2Digital Communication
11Electric Fields
11.1Electric Fields
12Current Electricity
12.1Current Electricity
13Magnetic Fields
13.1Magnetic Fields
14Modern Physics
14.1Quantum Physics
14.2Nuclear Physics
Jump to other topics
1Physical Quantities & Units
1.1Physical Quantities & Units
2Kinematics
3Dynamics
3.1Momentum & Newton's Laws of Motion
3.2Non-Uniform Motion
3.3Linear Momentum & Conservation
4Force, Density & Pressure
4.1Force, Density & Pressure
5Work, Energy & Power
6Deformation of Solids
7Waves
7.1Simple Harmonic Motion
7.2Waves
8Superposition
9Thermal Physics
9.1Circular Motion
9.2Thermal Physics
10Communication
10.1Communication Channels
10.2Digital Communication
11Electric Fields
11.1Electric Fields
12Current Electricity
12.1Current Electricity
13Magnetic Fields
13.1Magnetic Fields
14Modern Physics
14.1Quantum Physics
14.2Nuclear Physics
Practice questions on Atomic Model
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- 1What is the charge of an atom's nucleus?Multiple choice
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