GCSE Chemistry Unit 1 revision notes

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Topic 1- Atoms
Atoms are everywhere! Everything you see is made of atoms. Everything around us
is made of atoms. For your GCSE Chemistry Exams you must be able to structure
and draw atoms easily by looking at the periodic table.
You need to know that in an atom there are protons, neutrons and electrons.
Protons are POSITIVLEY charged and live in the centre of an atom with neutrons.
You can find the number of protons by looking at the atomic number of an atom.
There are the same numbers of electrons as protons.
Neutrons are NEUTRAL (hence the name). They live in the centre of an atom with
protons. To work out how many neutrons there are in an atom you look at the
atomic mass number (AM) of an atom take away the atomic number (AN) of the
atom. So the formula is: AM-AN=Neutrons.
Electrons are NEGITIVLY charged. They live in shells around the protons and
neutrons. They are EQUAL number to the amount of protons.
Take note that the middle of the atom with the protons and neutrons is also called
the nucleus
Here is a diagram of an atom:
Also atoms and elements (a type of atom) are ALL NEUTRAL CHARGED because there
are always the same numbers of protons as electrons. This only changes when a
chemical reaction takes place.

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You also need to understand these words mean:
Element- An element is a substance with one type of atom e.g.: Copper is an
element as it is only made of copper atoms.
Compound- A substance made from two types of atoms e.g.: Carbon dioxide
Mixture- A substance made from more than two types of atoms
How to draw atoms:
Drawing an atom is really easy, but to draw atoms you need to know the right
structure of an atom.…read more

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To make it easier, I will draw the atom shells one by one. Here is the first shell.
Remember Magnesium has 12 electrons!
We now are left with 10 electrons.…read more

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Exam Notes:
Make sure you know the electronic structure inside out ready for the exam. It is
vital that this is not forgotten as there are many questions likely to come in your
exam asking you to draw at least one type of element, compound, and mixture. If
you do not understand how I have drawn magnesium, keep reading it. You also have
to be able to recognise an atom drawing so read this page carefully.…read more

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Also take note that electron shells can also be called energy
levels, so don't be confused in exams if they use different terminology.
Make sure you also practice drawing elements. It is rare for you to draw compounds
and mixture but practice anyway and make sure you have the correct total of
electrons. Also make sure you have not put too many electrons in each shell.…read more

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I have colour coded the different groups. You need to know that the blue line
separates all the metals from the non-metals. So all the elements from the
right-hand side up to the blue line are all metals.
Another piece of important information you need to know is the fact that all
elements in the same group undergo similar chemical reactions and properties.…read more

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As the noble gases are uncreative they are uses in electric appliances e.g.: Argon in
used for the filament of a light bulb as it is unreactive and it passes electricity very
easily. It is very unlikely to create a bad reaction which can cause damages so it is
ideal for this purpose.
Neon is used in the same way- it is used for advertising as it glows and doesn't
cause a bad reaction when electricity passes through.…read more

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Topic 3- Ionic Bonding and Covalent Bonding
Ionic Bonding
You need to know that the elements that are the most reactive are the ones which
do NOT HAVE FULL OUTER SHELLS which determines what reaction an element
makes. The fact that they do not have full outer shells makes them want to react
with other elements to create a full shell.
This is where "Ionic Bonding" comes in. Ionic bonding is the chemical reaction
between a metal and non-metal.…read more

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Now you need to
remember that both these elements are reactive as they do not have full shells.
You also need to know that METALS ALWAYS GIVE ELECTRONS TO NON ­METALS. So
as Sodium (Na) is the metal, it gives its OUTER electron to Chlorine (Cl) which is the
non metal.…read more

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Now you need to do is put square brackets around the final elements and state
whether they are positively or negatively charged or neutral and by how many
electrons or protons. YOU NEED TO REMEMBER THAT THEY WILL NEVER BE NEUTRAL
AS THEY ARE EITHER GAINING OR LOSING ELECTRONS SO THIS WILL MAKE A
DIFFERENCE TO THE CHARGE. If an element gains an electron it becomes NEGATIVLY
charged as there is higher proportion of electrons than protons and electrons are
negatively charged.…read more

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