- 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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