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What is an atom?
Smallest part of an element that can exist
What is Dalton’s model of the atom?
Atoms as solid spheres that could be divided into smaller parts
What is the Plum pudding model of the atom?
Sphere of positive charge with negative electrons embedded in it
What did scientists discover in the alpha scattering experiment?
Some alpha particles were deflected by the gold foil - this showed that an atom’s mass and positive charge must be concentrated in one small space ( the nucleus)
Describe the nuclear model of the atom?
Dense nucleus with electrons orbiting it
What did Niels Bohr discover?
Electrons orbit in fixed energy levels (shells)
What did James Chadwick discover?
Uncharged particle called the neutron
Where are protons and the neutrons?
In the nucleus
What is the relative mass of each sub-atomic particle?
Proton: 1, neutron: 1, electron: 0 (very small)
What is the relative charge of each sub-atomic particle?
Proton: +1, neutron: 0, electron: -1
How can you find out the number of protons in an atom?
The atomic number on the Periodic Table
How can you calculate the number of neutrons in an atom?
mass number - atomic number
Why do atoms have no overall charge?
Equal numbers of positive protons and negative electrons
How many electrons would you place in the first, second and third shells?
Up to 2 in the first shell and up to 8 in the second and third shells
What is an element?
Substance made of one type of atom
What is a compound?
Substance made of more than one type of atom chemically joined together
What is a mixture?
Two or more substances not chemically combined
What are isotopes?
Atoms of the same element (same number of protons) with different numbers of neutrons
What are the four physical processes that can be used to separate mixtures?
Filtration, crystallisation, distillation, fractional distillation, chromatography
What is it meant by filtration
Note 
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