Topic
1
Elements and
Compounds
Topic
1
Pure substance or a mixture?
Topic
1
Two Types of Substances
• One type of pure substance can be broken
down into simpler substances. This type of
substance is called a compound.
• Another type of substance cannot be broken
down into simpler substances. Such a
substance is called an element.
• All the substances of the universe are either
elements, compounds formed from elements,
or mixtures of elements and compounds.
Topic
1
Two Types of Substances
• Of the known elements, only about 90 occur
naturally on Earth. The remainder are
synthesized, usually in barely detectable
amounts, in high-energy nuclear experiments.
• Less than half of the 90 naturally occurring
elements are abundant enough to play a
significant role in the chemistry of everyday
stuff.
Topic
1
Organizing the Elements
• The periodic table organizes elements in a
way that provides a wealth of chemical
information—much more than is evident to
you now. It shows the chemical symbols for
the elements.
• Their symbols usually correspond to their
names in Latin.
Topic
1
Periodic Table of the Elements
Topic
Compounds Are More Than One Element
1
• A more complete definition is that a
compound is a chemical combination of two
or more different elements joined together in a
fixed proportion with a unique set of chemical
and physical properties.
• More than 10 million compounds are known
and the number keeps growing.
Topic
Compounds Are More Than One Element
1
• Some new compounds are discovered and
isolated from natural chemical sources such as
plants and colonies of bacteria and are
synthesized in laboratories for many different
uses.
Topic
Compounds Are More Than One Element
1
• The properties of the compound are different
from the properties of the elements that
compose the compound.
silver
+
bromine = silver bromide
Topic
Compounds Are More Than One Element
1
• A formula is a combination of the chemical
symbols that show what elements make up a
compound and the number of atoms of each
element.
Compound
Formula
Caffeine
C8H10N4O2
Topic
Compounds Are More Than One Element
1
• Formulas provide a shorthand way of
describing a submicroscopic view of a
compound.
• You probably already use formulas like H2O
and CO2 as a way of talking about water and
carbon dioxide.
Topic
1
HOMEWORK
•Pg. 33 Section
Review Questions 15 (Copied on the
back of item # 21)