Download 5.3 Chemical Formulas - Merrell Science Room

Sugar- what is it made of?
Carbon- is usually found in pencils or
diamond jewelry
Hydrogen- is an extremely flammable gas,
used in space shuttles
Oxygen- is in air
When combined together it makes sugar
C6H12O6
Different elements combine with each other to
form different compounds.
5.2
Free atoms are rare in nature.
They usually are arranged in proportions.
Law of Constant Composition
All samples of a given compound have the same
proportions of their elements.
Lets look at water
If we decompose water we would find
16.0 g of oxygen to every 2.0 g of
hydrogen.
Mass ratio= 16.0gH/ 2.0g O= 8.0
This is true of any sample of water
Consider ammonia it contains 14.0 g of
nitrogen to every 3.0 g of hydrogen.
What is the mass ratio?
The mass ratio is always calculated by
dividing the larger mass by the smaller
one.
14.0/3.0= 4.7
5.3 Chemical Formulas
We represent compounds with a chemical
formula
H20
CO= carbon monoxide
this is an air pollutant
CO2= what we breath out
Chemical formulas usually list the most
metallic elements first.
NaCl
not
ClNa
What do I mean by most metallic?
There are few exceptions like hydroxide ion.
Write a chemical formula for the following.
a. The compound containing 2 aluminum
atoms to every 3 oxygen atoms.
b.The compound containing 3 oxygen atoms
to every 1 sulfur atom
c. The compound containing 3 chlorine
atoms to every 1 carbon atom
Some chemical formulas contain several
identical groups of atoms.
These groups are set in parenthesis and
are given a subscript to tell how many
Mg (NO3)2
Mg (NO3)2
How to determine the total number of each
type of atom.
Multiply the subscript outside the
parenthesis by the subscript for each atom
inside the parenthesis.
5.4 Molecular View of Elements and
Compounds
Atomic Elements- are those that exist in
nature with single atoms as their basic
units.
Helium
Copper
Mercury
Molecular Elements- do not normally exist in nature
as single atoms instead they exist as diatomic
molecules this mean two.
H2
O2
Cl2
Molecular Compounds- are compounds formed
between two or more nonmetals.
H2O
CO2
C3H6O
Ionic Compounds- compounds formed
between metal and on or more nonmetal
Metal tend to lose electrons
Nonmetals tend to gain electrons
Classify each of the following substances
as an atomic element, molecular element,
molecular compound, or ionic compound.
a.CoCl2
b.Nitrogen
c.SO2
d.KNO3
Write a chemical formula for the
compound containing 2 nitrogen
atoms to every 1 oxygen atom.
Determine the number of each
type of atom in Pb(ClO3)2
Classify each of the following as
atomic element, molecular
element, molecular compound, or
ionic compound.
a.Chlorine
b.NO
c.Au
d.Na2O
e.CrCl3