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Counting Atoms.

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Presentation on theme: "Counting Atoms."— Presentation transcript:

1 Counting Atoms

2 How to Count Atoms The symbol of an element represents one atom of that element. e.g. Na = 1 atom

3 A subscript is a number written at the lower right corner behind the symbol of an element. If there is more than one atom of the element, then a subscript is used to indicate the number of atoms. e.g. H2 = 2 atoms

4 A subscript outside a bracket multiplies all the elements inside the brackets.
e.g. Mg3(PO4)2 : Mg = 3 atoms P = 2 atoms O = 8 atoms Total Atoms: 13

5 (a) A coefficient is a number written in front of a chemical symbol and indicates the number of atoms of that element. e.g. 3 C = 3 atoms OR

6 (b) A coefficient is a number written in front of a chemical formula and indicates the number of that compound. NOTE: A coefficient multiplies the number of atoms of each element in the formula.

7 Examples 2 H2O 4 Hydrogen atoms 2 Oxygen atoms Total Atoms: 6

8 3 CuSO4 3 copper 3 Sulphur 12 Oxygen atoms Total Atoms: 18

9 4 Pb(NO3)2 4 lead 8 Nitrogen 24 Oxygen atoms Total: 36

10 Homework Complete two worksheets on counting atoms Remember:
Element Project is due Nov 2 3D box needs to be handed in after you give your 3 min presentation


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