Chemical Symbols and Chemical Symbols and FormulasFormulas
Chapter 2.7Chapter 2.7
Chemical SymbolsChemical Symbols All All elementselements in the in the Periodic TablePeriodic Table have have
symbols that are symbols that are recognized recognized world wideworld wide.. It does not matter which It does not matter which countrycountry you you
are in or the are in or the languagelanguage you speak. you speak. Example:Example: The element The element IronIron is always is always
identified by “identified by “FeFe” and ” and OxygenOxygen is “ is “OO”.”. The names are not always the same but The names are not always the same but
the symbols are. “the symbols are. “FeFe” is ” is iron in Canadairon in Canada, , fer in Francefer in France and and fier in Romaniafier in Romania..
Chemical SymbolsChemical Symbols
A A Chemical symbolChemical symbol is is an abbreviation of an abbreviation of a name of an a name of an element.element.
Capital letter if only Capital letter if only one letter.one letter.
Only first letter Only first letter capital if more than capital if more than one letterone letter
ElementElement Chemical Chemical SymbolSymbol
OxygenOxygen OO
NitrogenNitrogen NN
HydrogenHydrogen HH
SodiumSodium NaNa
SodiumSodium comes from the word comes from the word sodanum, a headache remedy, and sodanum, a headache remedy, and it’s symbol (it’s symbol (NaNa) comes from the Latin ) comes from the Latin word word NaNatrium.trium.
Chemical FormulasChemical FormulasA A chemical formulachemical formula is the combination is the combination
of symbols that represent a of symbols that represent a particular compound.particular compound.
The chemical formula indicates which The chemical formula indicates which elements are present in the elements are present in the compound and in what proportions.compound and in what proportions.
Ex. 1: Ex. 1: Water moleculeWater molecule
HH22OO: : 2 atoms of hydrogen, 1 atom of 2 atoms of hydrogen, 1 atom of oxygenoxygen
Ex. 2: Ex. 2: Iron Oxide moleculeIron Oxide molecule
FeFe22OO33: : 2 atoms of iron, 3 atom of oxygen2 atoms of iron, 3 atom of oxygen
Chemical Formulas - Chemical Formulas - ExamplesExamples
Calcium Carbonate (chalk) – CaCOCalcium Carbonate (chalk) – CaCO33
Sodium Chloride (salt) – NaClSodium Chloride (salt) – NaCl Acetysalicylic acid (aspirin) – CAcetysalicylic acid (aspirin) – C99HH44OO88
Acetic acid (vinegar) – CAcetic acid (vinegar) – C22HH44OO22
Chemical FormulasChemical Formulas
NOTESNOTES::
- Each - Each symbolsymbol in a in a formulaformula represents an represents an element.element.
- If only - If only one atomone atom of an element is present of an element is present in the compound, in the compound, nono subscript is used. subscript is used.
- If - If more than one atommore than one atom of an element is of an element is used, then the symbol is used, then the symbol is followed by a followed by a number indicating how many atoms are number indicating how many atoms are usedused. This is called the . This is called the subscript.subscript.
HomeworkHomework
Do Questions #1–5 on Page 59Do Questions #1–5 on Page 59 You may use your Periodic Table.You may use your Periodic Table. Make sure that for each question Make sure that for each question
you write out that question first then you write out that question first then you write your answer and then you write your answer and then continue on to the next question and continue on to the next question and so on until completed.so on until completed.
1 atom of sodium
2 atoms of hydrogen (in a hydrogen molecule)
3 atoms of magnesium2 atoms of phosphorus8 atoms of oxygen 13 total atoms
3 carbon atoms
TomorrowTomorrow
Go over counting atoms worksheetGo over counting atoms worksheet
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Chapter 2 quizChapter 2 quiz