Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Unit 1A
ACSChemistry in the CommunitySixth Edition
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Chemical Symbols and Formulas
UNIT 1.A.5-6 AND 7
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Mixtures, elements, compounds
Scientists like to classify things.
One way that scientists classify matter is by its composition.
Ultimately, all matter can be classified as mixtures, elements and compounds.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
By asking these questions scientists can classify matter into:
Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties. Solutions – a special kind of mixture where one
substance dissolves in another. Elements – simplest form of pure substance.
They cannot be broken into anything else by physical or chemical means.
Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Elements
Elements are the simplest pure substance. An element can not be changed into a simpler
substance by heating or any chemical process. The smallest particle of an element that
has the properties of that element is called an atom. An atom is the basic building block of matter.
There are more than one hundred known elements in the universe listed on the periodic table of elements. These elements combine in such a way to
create millions of compounds.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Elements
All elements are made of atoms.
Atoms of the same element are alike.
Atoms of different elements are different.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Elements
In 1813, a system of representing elements with symbols was introduced. Each symbol consists of
one or two letters. Two letters are needed for
a chemical symbol when the first letter of that element’s name has already been used.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Common Elements
Aluminum Al
Bromine Br
Calcium Ca
Carbon C
Gold Au
Helium He
Hydrogen H
Nitrogen N
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
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.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Chemical Symbols
A Chemical symbol is an abbreviation of a name of an element.
Capital letter if only one letter.
Only first letter capital if more than one letter
Element Chemical Symbol
Oxygen O
Nitrogen N
Hydrogen H
Sodium Na
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Sodium comes from the word sodanum, a headache remedy, and it’s symbol (Na) comes from the Latin word Natrium.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Compounds
Compounds are also pure substances.
But compounds are made from more than one element.
Water is a compound.
Water can be broken down into simpler substances – hydrogen and oxygen.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Chemical FormulasA 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
H2O: 2 atoms of hydrogen, 1 atom of oxygen
Ex. 2: Iron Oxide molecule
Fe2O3: 2 atoms of iron, 3 atom of oxygen
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Chemical Formulas - Examples
Calcium Carbonate (chalk) – CaCO3
Sodium Chloride (salt) – NaCl Acetysalicylic acid (aspirin) –
C9H4O8
Acetic acid (vinegar) – C2H4O2
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
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.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
I. CHEMICAL EQUATIONSA. Definitions 1. Chemical Equation - represents reactants and products in a reaction using symbols, formulas and coefficients. 2. Subscript - indicate the number of atoms of an element in a chemical reaction. 3. Coefficient - whole number in front of a formula or symbol that indicates the number of atoms, molecules, formula units or moles
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Subscripts vs. Coefficients
The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
CHEMICAL REACTIONS
Reactants: Zn + I2 Product: Zn I2
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Chemical Reactions
Chemical_Reactions.asf
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
B. Methods for Writing Equations
1. word equation – reactants and
products are represented by words
2. formula equation- reactants and
products are represented by
element
symbols and formulas
3. balanced chemical equation – a
formula equation using coefficients
to represent the number of atoms,
molecules, or formula units
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
C. Symbols Used in Writing Equations
1. --------> yields, forms, produces, reacts
to form 2. --------> reversible reaction (products <--------- react to re-form the
reactants)
3. symbols or words written above -----> a. triangle – reaction requires heat b. oC – indicates temperature required c. atm – indicate pressure is required d. symbol for element or formula for compound – catalyst is required
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
4. letters or symbols next to formula
a. letters
(s) – solid (l) – liquid
(g) – gas (aq) – aqueous solution
b. symbols
arrow point up – gas produced
arrow pointing down–precipitate forms
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Chemical EquationsChemical Equations4 Al(s) + 3 O2(g)
---> 2 Al2O3(s)
This equation means
4 Al atoms + 3 O2 molecules ---produces--->
2 molecules of Al2O3
AND/OR
4 moles of Al + 3 moles of O2 ---produces--->
2 moles of Al2O3
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
http://www.youtube.com/watch?v=d58UcB_Yb2Q
1. Define the terms “reactants” and “products.” Give examples of each from a chemical equation.
2. What do all chemical reactions need?
3. What do you think EA stand for?
4. What role does a catalyst play in a chemical reaction?
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
II. CHEMICAL REACTIONS
A. Bonds and Chemical Reactions
1. bonds form, break or both
2. atoms combine, separate, rearrange
A + B A-B C-D C + D
A-B + C C-B + A C-D + B C-B + D
A-B + C-D A-D + C-B