Aqa Chemistry C2 Higher Notes

here are my notes that i made for c2, aqa

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Zara Javed
C2 Notes
1 ­ Structures and Bonding
Number of electrons = Number of protons.
The number of protons in the nucleus of an atom is called the atomic number or
proton number (e.g. the atomic number of carbon is 6 and it has 6 electrons).
The lowest energy level is the shell nearest to the nucleus.
The highest energy level is the shell furthest from the nucleus.
The negative electrons are attracted to the positive nucleus. To move an electron
near the nucleus further away you need energy (to overcome the attractive force).
This makes the electrons further away have more energy.
The first shell contains 2 electrons and the rest hold 8 electrons.
Elements whose atoms have a full outer energy level are very stable and unreactive.
They are called noble gases.
Elements in the same groups have the same number of electrons in their highest
energy level (outer shell).
When you react 2 substances they make a compound and it's difficult to get the
substances back again.
Covalent bonding = Sharing electrons.
Ionic bonding = Transferring (giving or taking) electrons.
When an atom gains or loses electrons it becomes an ion. E.g. sodium has the
electronic structure 2, 8, 1. It needs to lose one so that it will become 2, 8. It is now
a sodium ion.
Ionic compounds are usually formed when metals react with non-metals.
Ionic compounds are held together by strong forces between the oppositely charged
ions. This electrostatic force of attraction is called the ionic bond.
Ionic bonds between charged particles result in an arrangement of ions that we call a
giant structure. This is a large number of atoms or ions arranged in a regular way,
because the ions all pack together neatly.
Covalent bonding ­ When non-metals react together, they share electrons to form
The atoms (or ions) in metals are arranged in regular layers.
The outer electrons in each atom can easily move from one atom to the next, in
Strong electrostatic attraction between the negatively charged electrons and
positively charged ions bond the metal ions together.
The sea of free electrons is called delocalised electrons.
The delocalised electrons are free to move throughout the metal lattice.
Metals are made up of small crystals called grains. The places where the grains join
are called the grain boundaries.

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Galvanising steel is when you dip iron (steel) in zinc to prevent it from rusting.
2 ­ Structures and Properties.
Ionic compounds have high melting and boiling points because the attractive forces
between the oppositely charged ions in the lattice are very strong, and there are lots
of them to overcome, so it takes a lot of energy to break the lattice apart.…read more

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Isotopes ­ atoms of the same element which have a different number of neutrons.
Sometimes extra neutrons make the nucleus unstable, so that it is radioactive. Not
all isotopes are radioactive. They just have a different mass.
Different isotopes of the same element have different physical properties. E.g. they
have a different mass and they may be radioactive. However they will have the same
chemical properties.
Relative atomic mass (Ar) is the same as the relative ionic mass.…read more

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Reacting masses:-
Write the equation Calcium + Oxygen calcium
Balance it 2Ca + O 2CaO
Work out the Ar + Mr 80 grams + 32 grams 112
Work out the missing mass 112 = 80 x = 21.…read more

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Exothermic reactions ­ They transfer energy from the reacting materials into the
surroundings. This causes an increase in temperature. E.g. respiration.
Endothermic reactions ­ They transfer energy from the surroundings into the
reacting materials. This causes a decrease in temperature. E.g. photosynthesis.
In a reversible reaction, one reaction is exothermic and the other is endothermic.…read more

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Ionic substances can be electrolysed when they are in molten or in solution, so
that the ions can move around freely.
OILRIG ­ Oxidation Is Loss, Reduction Is Gain.
Reduction and oxidation rake place at the same time so it is called a redox
When electrolysis happens in water, the less reactive element is usually produced
at an electrode.…read more

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Zara Javed…read more


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