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Atom Structure of the Atom -:
s The Nucleus:
· It contains protons and neutrons
· It has an overall positive charge because
neutrons are neutral and protons are positive.
· Almost the whole mass of the atoms is in the
· The nucleus is tiny compared to the rest of the
The Electrons:
· They move around the nucleus
· They have a negative charge.
· Tiny compared the nucleus.
· The size of their orbit depends on
the size of the atom.
· They occupy shells around the
nucleus (energy levels)…read more

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Number of Protons equal number of
otons, Neutrons and Electrons
· Neutral atoms have no overall charge.
Protons are heavy and · The number of protons always equals the
positively charged. number of electrons because the charge on the
electrons is the same size.
· The number of neutrons isn't fixed but is usually
Neutrons are about the same as the number of protons.
heavy and have no
Particle Relative Mass Relative Charge
Electrons are tiny Proton 1 +1
and negatively Neutron 1 0
Electron 1/2000 -1…read more

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Electron Shell Rules:
Elect 1) Electrons always occupy shells.
ron S
2) The lowest energy levels are always
filled first ­ the ones closer to the
It's as simple as one nucleus.
little duck and two fat
ladies... 3) Only a certain number of electrons
are allowed on each shell ­ 1st shell: 2
2nd shell: 8 3rd shell: 8
4) Atoms are much `happier' when they
2 8 8 are full electron shells.
5) In most atoms the outer shell isn't full
making them want to react.…read more

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Elem It's the number of protons in an atom that
ents decides what element it is ­ for example any
element that has 2 protons will be helium.
Lots of everyday substances are
Copper Atomic number and Mass Number...
Mass Number- Total
Aluminium number of protons and
· No two elements have the same neutrons.
atomic number this is what makes
them unique.
· To find out the number of neutrons
subtract the atomic number from
the mass number.
· The mass number is usually double
the atomic number.
Atomic Number ­
Number of protons
(also electrons).…read more

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es an Isotopes of the same element will have a
d Rel
Atom ative different mass number....
ic Ma
What are isotopes? Relative atomic mass takes isotopes into
­ account...
Relative atomic mass uses the average mass of the isotopes of an
Isotopes are element, it has to allow for the relative atomic mass of each isotope
and it's relative abundance.
different atomic
forms of the same Relative abundance means how much there is of the isotope
compared to the total amount of the element in the world.
element with the
same number of
Example: Work out the relative atomic mass of chlorine ...
protons but a
Multiply the mass of each
different number Element Relative Mass
of Isotope
abundance isotope by it's relative
of neutrons. Chlorine 35 3
Chlorine 37 1
Add those together.
Ar = (35 x 3) + ( 37 x 1) = 35.5 (nearest Divide by the sum of the
3+1 0.5) relative abundance.…read more

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