Chemical Symbols and Formulas Chapter 2 7 Chemical

Chemical Symbols and Formulas Chapter 2. 7

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

Chemical Symbols A Chemical symbol is an abbreviation of a name of an element. Element Oxygen Chemical Symbol O Capital letter if only one letter. Only first letter capital if more than one letter Nitrogen N Hydrogen H Sodium Na

Sodium comes from the word sodanum, a headache remedy, and it’s 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 u u u Calcium Carbonate (chalk) – Ca. CO 3 Sodium Chloride (salt) – Na. Cl Acetysalicylic acid (aspirin) – C 9 H 4 O 8 Acetic acid (vinegar) – C 2 H 4 O 2

Chemical Formulas NOTES: - 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 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. u

Homework Do Questions #1– 5 on Page 59 u You may use your Periodic Table. u Make sure that for each question you write out that question first then you write your answer and then continue on to the next question and so on until completed. u

1 atom of sodium 2 atoms of hydrogen (in a hydrogen molecule) 3 atoms of magnesium 2 atoms of phosphorus 8 atoms of oxygen 3 carbon atoms 13 total atoms

Tomorrow Go over counting atoms worksheet Pass in Homework Chapter 2 quiz