Structure and Bonding

AQA GCSE

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Atoms are made up of smaller subatomic particles
An atom contains a nucleus of protons and neutrons surrounded by orbiting electrons in
shells. Protons have a positive charge, electrons have a negative charge and neutrons have
no charge. The number of protons is equal to the number of electrons so the positive and
negative charges cancel out which is why atoms have no overall charge. The number of
protons in an atom is the atomic number, the number of protons and neutrons in an atom is
the mass number.
Proton +1 1
Neutron 0 1
Electron ­1 Negligible (0)
An atom contains a different number of electrons than protons is called an ion, a charged
particle, as the charges no longer cancel so the atom now has an overall charge.
An isotope is an atom of the same element with the same number of protons but different
number of neutrons.
An element consists of one type of atom only.
A compound is a substance which contains two or more elements chemically combined
together. The properties of a compound are different to the properties of the elements that
make them and they are also difficult to separate.
A molecule is two or more elements bonded together.
An atom is the smallest part of an element that can exist.
Atoms are arranged in the modern periodic table in order of ascending atomic number.
(Proton number.)
Elements in the same group have the same number of electrons in their outer shell which is
why the all have similar properties.
Elements in the same period have the same number of occupied shells e.g. period 3
elements will have 3 shells/orbits.
Electrons are arranged in different shells around the nucleus. The innermost shell is filled first.
Each shell can only hold a certain number of electrons before it gets full. (2,8,8) The number of
electrons in the outer shell also tell use what group the element belongs to e.g. 7 electrons in
the outer shell means it belongs to group 7. Atoms aspire to have a full outer shell in order to
become stable, like the noble gases. Most atoms do not have a full outer shell which makes
them want to react in order to gain one.

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Ionic bonding is the transfer of electrons
All elements aspire to be like the noble gases and gain a full outer orbit in order to be more
stable. They can go this gaining or losing electrons to gain a full outer orbit. This common for
elements who need to gain up to 3 electrons on need to lose up to 3 electrons for a full outer
orbit. Ionic bonding is only between nonmetals and metals.…read more

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Other examples of ionic compounds to be aware of ....
Calcium has two electrons to lose in order to gain a full outer electron and become more stable
whilst chlorine only needs to gain one electron to become more stable and have a full outer shell. In
which case calcium can still give away two electrons, but it gives away one to each chlorine atom.…read more

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Covalent Bonding
Covalent bonds form between nonmetal atoms and nonmetal atoms when they share
electrons in order to become stable by having a noble gas structure in which their outer
electron shell is full. They achieve full shells by covalent bonding.
Need to know how to draw diagrams
Hydrogen atoms only have one electron in their outer shell and aspire to be like the nearest
noble gas to be more stable, helium.…read more

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Practice drawing: ammonia, hydrogen, hydrogen chloride, chlorine, methane oxygen
Those were all examples of simple, molecular substances. (Simple means only small amount
of atoms present.…read more

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Metallic bonding
Metals form giant structures. Metal atoms have either two or three outer electrons. To get into
their stable noble gas structure they need to lose these electrons becoming positive ions.
When metal atoms are together in a piece of metal these outer electrons form a sea of free
electrons. These free electrons give metals their properties.
Since the electrons are negatively charged and the metal ions are positively charged an
electrostatic force of attraction is formed between them.…read more

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Nanomaterials ­ when smaller properties change for different uses
A nano metre (nm) is a billionth of a metre. Nano particles range from 1100 nano metres.
The manipulation of matter on a molecular scale(working with nano particles) is called
nanotechnology.
Nanoparticles have a large surface area (useful as catalysts) for their shape and volume
which gives them different properties and uses compared to larger materials of the same
substance.…read more

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