1.1. A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

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Last updated 10:53 PM on 6/11/26
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58 Terms

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What are atoms?
The smallest part of an element that can exist.
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What do atoms make up?
All substances.
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What do chemical symbols represent?
An atom of an element.
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What does Na represent?
One atom of sodium.
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How are compounds formed?
From elements by chemical reactions.
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What always happens in a chemical reaction?
One or more new substances are formed.
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What often accompanies a chemical reaction?
An energy change.
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What is a compound?
Two or more elements chemically combined in fixed proportions.
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Can compounds be separated by physical processes?
No.
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How can compounds be separated?
Only by chemical reactions.
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What is a mixture?
Two or more elements or compounds not chemically combined together.
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Do substances in a mixture keep their chemical properties?
Yes.
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How can mixtures be separated?
Filtration,crystallisation,simple distillation,fractional distillation,and chromatography.
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Are the methods used to separate mixtures physical or chemical?
Physical.
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Do physical separation processes produce new substances?
No.
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What did scientists first think atoms were?
Tiny spheres that could not be divided.
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What discovery led to the plum pudding model?
The discovery of the electron.
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What is the plum pudding model?
A ball of positive charge with negative electrons embedded in it.
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Which experiment led to the nuclear model?
The alpha particle scattering experiment.
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What was fired at the gold foil?
Alpha particles.
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What happened to most alpha particles?
They passed straight through.
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What happened to some alpha particles?
They were deflected at different angles.
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What happened to a very small number of alpha particles?
They came straight back.
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Why were alpha particles deflected?
They were repelled by a small positively charged nucleus.
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What did the alpha scattering experiment show?
Most mass is concentrated in a small positively charged nucleus.
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Who suggested electrons orbit the nucleus at specific distances?
Neil Bohr.
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What did Bohr propose?
Electrons orbit the nucleus in specific energy levels.
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What did later experiments show positive charge was made of?
Protons.
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Who provided evidence for neutrons?
James Chadwick.
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What is the atomic number?
The number of protons in an atom.
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Do all atoms of the same element have the same number of protons?
Yes.
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Why are different elements different?
They have different numbers of protons.
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What is the relative charge of a proton?
+1.
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What is the relative charge of a neutron?
0.
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What is the relative charge of an electron?
-1.
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Why does an atom have no overall charge?
The number of protons equals the number of electrons.
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What is the approximate radius of an atom?
About 0.1nm.
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How large is the nucleus compared with the atom?
Its radius is less than 1/10000 of the atom's radius.
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Where is almost all of an atom's mass found?
In the nucleus.
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What is the relative mass of a proton?
1.
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What is the relative mass of a neutron?
1.
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What is the relative mass of an electron?
Very small.
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What is the mass number?
The number of protons plus neutrons.
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How do you calculate mass number?
Protons+neutrons.
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What are isotopes?
Atoms of the same element with different numbers of neutrons.
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Do isotopes have the same number of protons?
Yes.
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How do isotopes differ?
They have different numbers of neutrons.
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What is relative atomic mass?
A weighted average that takes account of isotope abundance.
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Why is relative atomic mass often not a whole number?
Because it is a weighted average.
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How do you calculate relative atomic mass?
((Isotope mass×abundance)+(Isotope mass×abundance)+...)÷100.
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Which energy levels do electrons occupy first?
The lowest available energy levels.
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What does electronic structure show?
How many electrons are in each shell.
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What is the electronic structure of sodium?
2,8,1.
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How many electrons are in the first shell of sodium?
2.
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How many electrons are in the second shell of sodium?
8.
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How many electrons are in the third shell of sodium?
1.
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What do the numbers in an electronic structure represent?
The number of electrons in each shell.
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