What is the plum pudding model?
An atom with electrons embedded in a positive mass
Who created the plum pudding model?
J.J. Thomson
Where is the mass in the plum pudding model?
Spread evenly throughout the atom
Where are the charges in the plum pudding model?
Negative electrons embedded in positive mass
Explain the 4 key points of J.J. Thomson’s atomic model
Mass is spread evenly; positive charge is spread throughout; electrons are embedded in the positive mass; no nucleus
What did Rutherford discover about the atom?
Most of the atom is empty space
Where is the mass in Rutherford’s model?
Concentrated in a tiny nucleus
Where is the positive charge in Rutherford’s model?
In the nucleus
What do electrons do in Rutherford’s model?
Move around the nucleus
Explain the 4 key points of Rutherford’s atomic model
Most of atom is empty space; mass is concentrated in a tiny nucleus; nucleus is positively charged; electrons orbit the nucleus
What is special about Bohr’s model?
Electrons orbit at fixed distances (energy levels)
Where is most of the mass in Bohr’s model?
In the positively charged nucleus
What are energy levels?
Fixed orbits where electrons exist
How do electrons move in Bohr’s model?
In set orbits around the nucleus
Explain the 4 key points of Bohr’s atomic model
Electrons orbit at fixed distances; these are energy levels; electrons do not exist between levels; energy is absorbed or emitted when electrons change levels
What is the modern atomic model?
A nucleus with protons and neutrons, electrons in energy levels
Where is most of the mass in the modern model?
In the nucleus
What particles are in the nucleus? (Modern’)
Protons and neutrons
What is the arrangement of electrons in the modern model? (Modern)
In fixed energy levels (shells) around the nucleus
Explain the 4 key points of the modern atomic model
Nucleus contains protons and neutrons; most mass is in nucleus; electrons are in energy levels; most of atom is empty space
Gold foil experiment
Who did the experiment?
3 results and 3 conclusions made
Ernest Rutherford
1. Most of the alpha particles went straight through the foil; this showed that most of the atom is empty space.
2. Some of the particles deflected straight back; this meant most of the mass was concentrated in a tiny central nucleus.
3. Some alpha particles get deflected at an angle; this meant the nucleus must have a positive charge whoch repelled the positive charged alpha particles.
