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Counting Atoms. Vocabulary and Steps. Chemical Symbol. Usually a one- or two-letter set of characters that is used to identify an element. Examples: H, He, Ne, W, Li, Ag. Compound Formula. A combination of symbols that shows the ratio of elements in a compound.
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Counting Atoms Vocabulary and Steps
Chemical Symbol • Usually a one- or two-letter set of characters that is used to identify an element. • Examples: H, He, Ne, W, Li, Ag
Compound Formula • A combination of symbols that shows the ratio of elements in a compound. • Example: H2O (two hydrogen : one oxygen)
Subscript • Shows the number of atoms of an element in a molecule or the ratio of elements in a compound. • No subscript means one. • Example: H2O • The two is the subscript for hydrogen so there are two hydrogens • Oxygen has no subscript so there is one oxygen
Coefficient or Pre-Script • A number placed in front of a chemical formula in an equation. • No coefficient means one. • Example: 6CO2 • Six is coefficient, it is used for all the elements of the compound or molecule. • There are six carbons and twelve oxygens in the formula above.
Counting ‘em Up!! • If there is a subscript, but no coefficient use the subscript for the element. • H2O (2 hydrogen, 1 oxygen) • If there is a coefficient, but no subscript use the coefficient for every element . • 2AgS (2 silver, 2 sulfur) • If there is a subscript and a coefficient multiply the coefficient by the subscript for each element. • 12CO2 (12 carbon, 24 oxygen)