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Summary atomic structure and the periodic table GCSE chemistry revision notes
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All you need for GCSE chemistry revision topic - atomic structure and the periodic table exam board: Pearson Edexcel GCSE
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Atomic structure-An atom is the smallest type of an element that can exist
the Dalton model suggested that an atom was a solid sphere, although it correctly identified
that all matter is made up of atoms, atoms can’t be broken down into smaller parts, all
atoms in an element are identical, this was proved incorrect after the discovery of
subatomic particles- electrons.
At the centre of an atom is its nucleus (very small relative to the rest of the atom) which
contains neutrons and protons, fast moving electrons surround this in electron shells at
different distances from the nucleus.
Protons- +1 mass= 1
Electrons- -1 mass= 1/1835 (negligible)- so small it can be ignored
Neutrons- 0 mass= 1
Atoms contain equal numbers of electrons and protons because they have no overall charge
so they must cancel each other out.
Most of the mass of an atom is concentrated in the nucleus
Number of protons = atomic number
Number of neutrons = mass number – atomic number
Number of electrons = atomic number
Mass number = number of protons + number of neutrons in nucleus
Atomic number = number of protons in nucleus
All atoms of an element have the same number of protons in the nucleus and that number
is unique to each element.
Isotopes-
Isotopes are atoms of the same element which have different masses (they have the same
atomic number but different mass numbers)
Isotopes are different atoms of the same element containing the same number of protons
but different numbers of neutrons in their nuclei.
Isotopes of the same element are chemically identical as they have the same number of
protons and electrons.
Nuclear fission is when a nucleus is split; this produces new elements and transfers huge
amounts of energy.
Relative atomic mass = total mass of the atoms / the number of atoms
E.g. the abundances of two isotopes of chlorine are 75% of Cl-35 and 25% of Cl-37
Take 100 atoms= (75 x 35) +(25 x 37) / 100
The periodic table-
in 1869 Mendeleev published a table which organised the elements, this led directly to the
modern periodic table.
At the time there were 63 discovered elements and Mendeleev organised them in order of
increasing relative atomic mass, unlike others in previous attempts Mendeleev left gaps in
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