Unit 1A
ACS
Chemistry in the
Community
Sixth 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
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.


The smallest particle of an element
that has the properties of that
element is called an atom.


An element can not be changed into a
simpler substance by heating or any
chemical process.
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
Bromine
Calcium
Carbon
Gold
Helium
Hydrogen
Nitrogen
Al
Br
Ca
C
Au
He
H
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.
Element
Oxygen
Chemical
Symbol
O
Capital letter if only
one letter.
Nitrogen
N
Hydrogen
H
Sodium
Na
Only first letter
capital if more than
one letter
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 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
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 EQUATIONS
A. 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
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 Equations
4 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
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
ductile
Not ductile
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers
Watch periodic tables:
http://www.periodicvideos.com/
Unit 1A | ACS Chemistry in the Community, Sixth Edition | ©2012 BFW Publishers