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atoms, ions
&

Module 2: Foundations in Chemistry

compounds

A proton has virtually the same mass as a neutron, of 1
...
A proton has a charge of 1+, whilst an electron has a charge of 1-,
and a neutron has a charge of 0/neutral
...
Different elements contain atoms
that have different numbers of protons
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Hydrogen Isotopes

isotopes
isotopes
Hydrogen-1

Hydrogen-2

Every atom of an element has the same number of protons
...

There may be small differences in physical properties, with higher mass isotopes of an element
having a higher melting point, boiling point and density- but the chemical reactions are the
same
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The number of electrons is different from the number of protons
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Anions have an overall negative charge

Cation- Li+

relative mass

Anion – F-

Relative mass (atomic), Ar, is the weighted mean mass of an atom of an element compared with 1/12th of the mass of an
atom of carbon-12
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determination of ar
The percentage abundances of the isotopes in a sample of an element are found experimentally using a
mass spectrometer
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A sample is placed in the mass spectrometer
2
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The ions are accelerated
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4
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Each ion reaching
the detector adds to the signal, so the greater the abundance, the larger the signal
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#$%&'()$ /0
$ ,- (,
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g
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78% of chlorine-35 and 24
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Ar of chlorine =

((75
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22 × 37))
100

ions & molecules
1+



2+

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