Section 8.1
Matter
Pure
Substances
Elements
Mixtures
Compounds
Molecular
Homogenous
Ionic
Heterogeneous
Common Molecules
 www.reciprocalnet.org/edumodules/commonmolecul
es/element/list.html#simple
Molecules and Molecular
compounds
 Covalent bond- atoms held together by the sharing of
electrons
 What is the difference between an ionic compound
and a molecular compound?
Examine this picture of NaCl in H2O
 Ionic compounds are made of + and – charged ions
arranged in repeating 3-D patterns ex: NaCl
 Molecular compound is made of elements chemically
combined ex: H2O
 Molecular compounds have lower melting and boiling
points than ionic compounds
Molecular formulas
 Molecular formula-chemical formula of a molecular
compound that shows how many atoms of each element
are in a molecule
 NOTE: this reflects actual # of atoms-not whole number
ratio
 Ex: H2O
 Subscript (2) after the H indicates there are 2 hydrogen
atoms and one oxygen atom
How many carbon and oxygen atoms are in a molecule of
CO2?
 Chocolate chip cookie recipe:






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2 eggs
1 cup sugar
1 cup brown sugar
2 cups chocolate chips
1 tsp vanilla
2 cups flour
If I change the recipe-add peanut butter chips instead of
chocolate chips, the cookies are different
In a molecular formula, the subscripts tell you the number of
atoms of each element in a compound
 Diagrams and models
Ex:Ammonia
 Molecular formula- NH3
 Structural formula-
 Space filling molecular model
 Ball and stick molecular model
 Perspective drawing

In plane

Coming forward

Going backwards
Bond going across the back
 Molecule-a neutral group of atoms joined together by
covalent bonds
 Diatomic molecule- a molecule consisting of two of
the same atoms
 Carbon is black, oxygen is red….
What is the formula of this
molecule?
 What are the molecular formulas for these
molecules?
TRUE OR FALSE:
 All compounds contain molecules.
FALSE
There are no elements that exist as
molecules.
FALSE
Most molecular compounds are
composed of two or more
nonmetallic elements.
TRUE
Atoms in molecular compounds
share electrons.
TRUE
Molecular compounds tend to have
higher melting and boiling points
than ionic compounds
FALSE
 Which of the following formulas represent
molecules?
 Br2
 KBr
 CH4
 SO3
 N2H2
 Ne2
Answer: Br2, CH4, SO3, N2H2
 Which of the following formulas represent
compounds?
 Br2
 KBr
 CH4
 SO3
 N2H2
 Ne2
Answer: KBr, CH4, SO3, N2H2