The Atom Flashcards
Name the three types of particles found in an atom.
Proton
Neutron
Electron
Give the relative masses of the particles found in an atom.
Proton- 1
Neutron- 1
Electron- 1/2000
State where in an atom the sub atomic particles will be found?
Proton and neutrons are found in the nucleus, the electron is found in the outer shells
What is mass number?
The total number of protons and neutrons in an atom.
What is atomic number?
The total number of protons in an atom.
How can you work out the number of neutrons an atom has?
Subtract the atomic number from the mass number.
What are isotopes?
Any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights.
Explain why isotopes can have different physical properties.
Physical properties depend on the mass of the atom. Isotopes have different masses and so have different physical properties.
Describe how JJ Thompson’s model of the atom was different from Dalton’s model.
Dalton described atoms as solid spheres. JJ Thomson suggested they were not solid spheres- he thought they contained negatively charged particles (electrons) in a positively charged “pudding”.
What name was given to JJ Thomson’s model of the atom?
The plum pudding model.
Name the scientists who conducted the gold foil experiment in 1909.
Ernest Rutherford, Hans Geiger and Ernest Marsden.
Explain how the gold foil experiment provided evidence that Thomson’s model was wrong.
If Thomson’s model was correct the alpha particles fired at the shell of gold should have been deflected slightly by the positive “pudding” that made up most of the atom. Instead, most of the alpha particles passed straight through the gold atoms, and a very small number were deflected backwards. So the plum pudding model couldn’t be right.
Describe Rutherford’s model of the atom.
Rutherford’s model has a tiny positively charged nucleus at the centre surrounded by a “cloud” of negative electrons. Most of the atom is empty space.
Describe the main features of Bohr’s model of the atom.
In Bohr’s model the electrons only exist in fixed shells and not anywhere in between. Each shell has a fixed energy. When an electron moves between shells electromagnetic radiation is emitted or absorbed. Because the energy of the shells is fixed, the radiation will have a fixed frequency.
Is the Bohr model of the atom a true representation of the structure of the atom?
No.
