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.6 AND 7

Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers

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 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

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

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

Chemical Reactions

Chemical_Reactions.asf

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

CHEMICAL REACTIONS

Reactants: Zn + I2 Product: Zn I2

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

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