Chemical Symbols and Formulas

Chemical Symbols  All elements in the Periodic Table have symbols that are recognized world wide.  It does not matter which country you are in or the language you speak.  Example: The element Iron is always identified by “Fe” and Oxygen is “O”.  The names are not always the same but the symbols are. “Fe” is iron in Canada, fer in France and fier in Romania.

Chemical Symbols A Chemical symbol is an abbreviation of a name of an element. Capital letter is used if the symbol has only one letter. Only first letter capitalized if there is more than one letter. Element Chemical Symbol OxygenO NitrogenN HydrogenH SodiumNa

Chemical Symbols Chemical Symbols are often the first letter of the element name. However, some chemical symbols come from the Latin name of the element. Sodium comes from the word sodanum, a headache remedy, and its symbol (Na) comes from the Latin word Natrium.

Chemical Formulas A chemical formula is the combination of symbols that represent a particular compound. The chemical formula indicates which elements are present in the compound and in what proportions. Ex. 1: Water molecule H 2 O: 2 atoms of hydrogen, 1 atom of oxygen Ex. 2: Iron Oxide molecule Fe 2 O 3 : 2 atoms of iron, 3 atom of oxygen

Chemical Formulas - Examples  Calcium Carbonate (chalk) – CaCO 3  Sodium Chloride (salt) – NaCl  Acetylsalicylic acid (aspirin) – C 9 H 4 O 8  Acetic acid (vinegar) – C 2 H 4 O 2

Coefficients and Subscripts  A coefficient is a number written in front of a chemical formula to indicate how many of that compound is present.  A subscript is a number that is written in the lower right hand corner behind the symbol of an element. If there is more than one atom of the element present, then a subscript is used to indicate how many are present.

Chemical Formulas  NOTES: - Each symbol in a formula represents an element. - Each symbol in a formula represents an element. - If only one atom of an element is present in the compound, no subscript is used. - If only one atom of an element is present in the compound, no subscript is used. - If more than one atom of an element is used, then the symbol is followed by a number indicating how many atoms are used. This is called the subscript. - If more than one atom of an element is used, then the symbol is followed by a number indicating how many atoms are used. This is called the subscript.

Subscripts

Coefficients and Subscripts

Let’s Practice - Let’s Practice - Na 2 CO 3 Type of Atom# of Atoms Sodium 2 Carbon 1 Oxygen 3 Total6

CO 3 (PO 4 ) 2 Type of Atom # of Atoms Carbon1 Oxygen11 Phosphorus2 Total14

K 2 CrO 4 Type of Atom # of Atoms Potassium2 Chromium1 Oxygen4 Total7

3BaCl 2 Type of Atom # of Atoms Barium3 Chlorine6 Total9

NH 4 C 2 H 3 O 2 Type of Atom # of Atoms Nitrogen1 Hydrogen7 Carbon2 Oxygen2 Total12

4Al 2 (CO 3 ) 3 Type of Atom # of Atoms Aluminum8 Carbon12 Oxygen36 Total56

Pb(NO 3 ) 2 Type of Atom # of Atoms Lead1 Nitrogen2 Oxygen6 Total9

2(NH 4 ) 2 Cr 2 O 7 Type of Atom # of Atoms Nitrogen4 Hydrogen16 Chromium4 Oxygen14 Total38