- All substances are made from atoms.
- Each atom is made from a nucleus - containing protons and neutrons - which is orbited by electrons.
- The atomic number is the number of protons in the atom. The elements in the periodic table are ordered by atomic number.
- The atomic mass is the total number of protons and neutrons.
- An atom is 1 single thing.
- A compound is 2 or more atoms bonded together - the atoms must be different.
- A molecule is 2 or more of any atom bonded together - the atoms can be the same
- In a atom, the number of protons equals the number of electrons.
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Protons, Neutrons and Electrons
- At the centre of every atom is a nucleus containing protons and neutrons.
- Electrons are contained in shells around the nucleus.
- The number of electrons is always the same as the number of protons in the nucleus.
- Each proton has an electrical charge of +1
- Each electron has an electrical charge of -1
- Each neutron has no charge meaning it is neutral.
- An atom has the same number of protons as electrons meaning the overall charge is 0 (neutral)
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- The little numbers apply only to the letter before them. eg; CH4 = 1 carbon and 4 hydrogen.
- The big numbers apply to the whole of that part of the equation after them. eg; 2H2O = 4 hydrogens and 1 oxygen
- The atoms are the amount of each element and the elements are the amount of letters there are.
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- A balanced equation si a symbolic representation showing the kind and amount of the starting materials and products of a reaction. There is the same amount of each element on each side of the equation. eg; 2Na + Cl2= 2NaCl is a balanced equation.
- To balance an equation you can only change the big numbers not the little ones. eg; Na + Cl = 2NaCl would become 2Na +2Cl = 2NaCl.
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