Elements and Compounds
Elements
o
An element is a pure
substance
o
An element is made of
only one type of atom (ex; Na, Cl, H, O)
o
An element cannot be separated into simpler substances by chemical or
physical means
o
Each element has its own
unique properties
o
All matter is composed
of one or more of approximately 118 elements
o
Ten elements make up
99+% of the mass of the Earth's crust, oceans and atmosphere.
o
When writing element
symbols:
o
the first letter is
always capitalized
o
the second letter is
always lower case
Compounds
o
A compound is made of
molecules (2 or more different atoms, ex: NaCl, H2O)
o
Compounds are formed by chemically
combining two or more elements
o
The compound created by
combining two or more pure substances is a new pure substance
o
Compounds have
properties that are different from the elements that make them
o
Compounds have their own
unique properties
o
Compounds can be
separated into elements only by chemical change with heat or electric current
o
Compounds cannot be
separated by physical means