AQA Chemistry 1 C1.1

Atoms

All substances are made out of atoms and a substance made out of one type of atom is an element.
Atoms have a central nucleus, made up of neutrons and protons, and electrons surround the nucleus.
A Proton has a charge of +1, a neutron has a charge of 0 (neutral) and electrons have a charge of -1.
There is an equal number of protons to electrons in an atom so an atom has a charge of 0.
Each element has atoms with the same number of protons. Atoms of different elements have different numbers of protons.
Electrons in an atom are organised into energy levels or shells. They fill the inner shells first and then move further out.

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There are around 100 elements in the periodic table.
The elements are organised into groups based on the number of electrons on their outer shells.
Elements in each of the groups have similar chemical properties.
There are 8 groups going from 0 to 7 electrons on their outer shell.
The elements in group 0 are known as the noble gases.
Noble gases are nonreactive because they have stable arrangements of electrons.
Each element in the periodic table is shown by it's chemical symbol such as oxygen which is O.
It also shows the Proton Number ( number of protons) and Atomic Mass (sum of the protons and neutrons)
The number of protons will be the same as the number of electrons.

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Atoms join with other atoms to form compounds when they react.
They may give, take or share electrons to form ions or molecules.
When metals and non-metals react, it is ionic bonding so they give and take electrons.
Metals lose electrons to form positive ions.
Non-metals gain electrons to form negative ions
When non-metals react, it is covalent bonding so they share electrons.
Recation can be shown by word and symbol equations.
Atoms cannot be lost or made during reactions so the mass of all the products is the same as the mass of the reactants (outcome)

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