C2 Exhaustive Revision Notes

These are my exhaustive revision notes for Chemistry Unit 2 of the GCSE Additional Science / GCSE Chemistry syllabus for Edexcel.

I have used multiple textbooks as well as internet sources to compile these notes, and whilst I was compiling them, I actively kept the syllabus at hand, so hopefully there is nothing beyond these notes which is essential knowledge in order to answer any question on the exam paper (I would promise, but I know everyone's liable to human error!).

I hope that you may find these notes useful :)

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By the 1860s, 63 elements were known and chemists were eager to make a table organising the elements in a
helpful way.
In 1869, Russian chemist Dmitri Mendeleev (1834-1907) organised a table in order to help him discern which
order to study the elements in within the second volume of his chemistry textbook. He produced the first
periodic table, in which:
Elements were arranged in order of increasing atomic weight (later replaced by the atomic number) ,
allowing for some exceptions for the next bullet point (e.g.iodine
Elements with similar chemical properties were arranged into the same group .
Gaps were left for undiscovered elements with predicted chemical properties based on those of nearby
elements : Mendeleev believed that not all of the elements had been discovered, unlike many of his
Mendeleev continued to refine his table for years afterwards. It was proved to be useful in 1875 when gallium
was discovered: Mendeleev had predicted an element (which he called eka-aluminium) with similar chemical
properties to a significant degree of accuracy based on gaps in his periodic table.
In the modern-day periodic table:
Elementsare arranged in order of increasing a
tomic number in rows (called periods ).
Elementswith similar chemical properties are arranged in vertical columns (called groups).
All matter is made up of atoms . Each atom has a nucleus (central part) composed of neutrons and protons ,
collectively called nucleons , which are subatomic particles with neutral and positive charges respectively. Each
proton and electron has a relative mass of 1.
The diameter of the nucleusis 100,000 times smaller than the diameter of the atom, which is 2x10-7
Electrons, discovered in 1898 by J.J. Thomson, are subatomic particles with negative charges which move
around the atomic nucleus in rings known as s
hells. Each e
lectronhas a negligible relative mass.
Subatomic Relative
Relative mass
particle charge
Protons +1 1
Neutrons 0 1
Electrons -1
Atoms have the same number of neutrons and electrons, so they have no overall charge.
If they gain or lose an
electron, they instead become charged. A charged atom
is known as an i
Each elementis shown in the periodic table alongside its atomic number,mass number and symbol.
The symbol of an atom is an internationally-recognised abbreviation up to two letters long which identifies the
element. The first letter is always a capital letter the second letter is lowercase if it exists.
All atoms in an element have the same number of protons (and thus electrons). The number of protons in an
atom is called the proton number, or the a
tomic number.
Because both protons and neutrons have a relative mass (whilst that of neutrons is negligible), the atomic
number of an atom is always lower than its nucleon number (or mass number ), which is the addition of the
number of protons and the number of n
eutrons in an atom.
number of neutrons in an atom = mass number ­ atomic number
Whilst two atoms of the same element will always have the same atomic number because they will always have
the same number of neutrons, the number of neutrons between two atoms of the same element may vary (and

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Atoms of the same element which have different numbers of neutrons are
called isotopes.
Isotopes of the same element have the same chemical properties because they have the same number of
Some periodic tables show the relative atomic mass of elements as opposed to their mass number . The relative
atomic mass of an element considers the different mass numbers of different isotopes of the element as well
as their relative abundances.…read more

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In order to form the ionic compound of potassium sulphide, the potassium atom must lose one electron because
it has an electronic configuration of whilst the sulphur atom must gain two electrons because it has an
electronic configuration of 2.8.6. Two atoms of potassium are therefore needed to give away two electrons
collectively to one atom of sulphur so as to form the ionic compound of potassium sulphide the chemical
formula of the ionic compound is therefore K 2S.…read more

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Electrical conduction . Ionic compounds conduct electricity only when molten or dissolved in an aqueous
solution because they have no delocalised electrons as solids the crystal lattice structure means that all
electrons are held firmly in place.…read more

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Barium Pale green
Calcium Brick red
Copper Blue/green
Carbonates will effervesce (fizz) if dilute hydrochloric acid is added to them. This gives off carbon dioxide,
which turns limewater milky if bubbled through it.
If dilute hydrochloric acid and a few drops of barium chloride are added to a sulphate, a white precipitate ­
barium sulphate, the self-same used in barium meals ­ will form.…read more

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Most simple molecular covalent substances are i
nsolublewith some exceptions, such as sucrose.
As opposed to simple molecular covalent substances, some covalent substances form large networks of atoms .
These are known as giant molecular covalent substances and include diamond and graphite , both of which are
forms of pure carbon .
Both diamond and graphite have high melting and boiling points as a result of the many strong covalent bonds
within them.…read more

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As the solvent then soaks up the chromatography paper, it carries the mixture upwards with it. Because
different components of the mixture will move at different rates, the mixture separates out along the
chromatography paper .
The chromatography paper , now known as the chromatograph ,shows the spots for the separate components of
the original mixture over time. The chromatograph is removed from the container and dried.…read more

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Are strong and hard: the strength of the electrostatic attraction between their cations and delocalised
electronsgives metals this property.
3. Are malleable: the layers of cations can slide over each other but are still held together by their
electrostatic attraction with the delocalised electrons, so metals bend and stretch without breaking.
4. Can conduct electricity: the sea of delocalised electrons allows currents to flow through metals when a
voltageis applied.
Most metals are transition metals.…read more

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Halogens attract outer shell electrons from elements which do not have a tight hold on them, such as alkali
metals. This produces ionic compounds because the halogens take electrons from the elements to form ions .
Halogens can reach a stable electronic configuration i
n this manner.…read more

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Chemical reactions which give out thermal energy to the surrounding environment are called exothermic
reactions. Most chemical reactions are exothermic reactions.
Combustion reactions , precipitation reactions, metal displacement reactions , neutralisation reactions and
explosions are exothermic reactions. For example, the c
ombustionin a cars engine releases thermal energy .
Thermal energy is absorbed from the surrounding environment when chemical bonds are broken the process is
endothermic.Thermal energy is released when chemical bonds are formed the process is exothermic.…read more



Great notes :)


brilliant :)


amazing, thanks


great revision cards really useful :)))))

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