What are all elements made up of?
What does an atom consist of?
A nucleus containing protons and neutrons surrounded by electrons
What is the relative mass of a proton?
What is the relative mass of a neutron?
What is the relative mass of an electron?
What is the relative charge of a proton?
What is the relative charge of a neutron?
What is the relative charge of an electron?
Describe John Dalton’s model of the atom.
At the start of the 19th Century, John Dalton described atoms as solid spheres, and said that different spheres made up the different elements
Describe J.J. Thompson’s model of the atom
In 1897 J.J. Thompson concluded from his experiments that an atom most contain even smaller, negatively charged particles - electrons. The new model was known as the plum pudding model
Describe Rutherford’s model of the atom.
In 1909, Ernest Rutherford conducted the Gold Foil Experiment. He fired alpha particles (+ve) at a very thin sheet of gold. They were expecting most of the particles to be deflected slightly by the positive pudding that made up most of an atom. But most of the alpha particles passed straight through, and only a small number of particles were deflected. So Rutherford came up with the Nuclear Model. In this, there’s a tiny positively charged nucleus at the centre, surrounded by a cloud of negative electrons. Most of the atom is empty space
Describe Niels Bohr’s model of the atom.
- Electrons only exist in fixed orbits (shells)
- Each shell has a fixed energy
- When an electron moves between shells, electromagnetic radiation is emitted or absorbed
- Because the energy of shells is fixed, the radiation will have a fixed frequency