Applied Chemistry
Mr. Gensits
Class Notes 9/17/2014
Elements and Compounds
Element - the simplest form of matter that has a unique set of
properties
Elements cannot be separated into simpler substances by
chemical means.
Elements are the building blocks for all other substances
There are now 118 known elements (as of 2010).
All elements after uranium on the periodic table are man-made.
A compound is a substance that contains two or more different
elements chemically combined in a fixed proportion.
A compound can be separated into simpler substances only by
chemical means.
Chemical Change
A change that produces matter with a different composition than
the original matter.
There is no chemical process that will break an element down into
simpler substances.
Properties of Compounds
In general, the properties of compounds are different from
those of their component elements.
Sodium – soft, grey metal
Chlorine – pale yellow-green poisonous gas
Sodium chloride (table salt) – white crystalline solid
Distinguishing Substances (element, compound) and Mixtures
If the composition of a material is fixed, the material is a
substance.
If the composition of a material may vary, it is a mixture.
Chemical Symbols
Each element is represented by a one- or two-letter symbol.
The first letter of the symbol is always capitalized.
If there is a second letter, it is always lowercase.
Examples:
Co – cobalt (element)
CO – carbon monoxide (compound)
NaCl – sodium chloride (compound)
Si – silicon (element)
SI2 – sulfur iodide (compound)