Elements, Compounds, &
Chemical Names
Elements
• A pure substance that cannot be separated into a simpler substance
by physical or chemical means.
• Elements are the building materials of all matter.
-Of the 118 known elements, only 92 are
known to occur naturally in nature.
Compounds
Pure substance composed of two or more different elements
joined by chemical bonds.
• Made of elements in a specific ratio
that always has the same chemical formula
• Can only be separated by
chemical means, not physically
*Compounds can be very different in appearance and behavior from
the elements that they are composed of.
Ex: Sodium (Na) combined with chlorine (Cl) makes the compound
sodium chloride (NaCl)
Reaction of pure sodium with water…… a very violent reaction!
Mixtures
• A combination of two or more pure substances that are not chemically
combined.
• substances held together by physical forces, not chemical
• Each item retains its properties
in the mixture
• They can be separated physically
Element, Compound, or
Mixture?
Jelly Beans
Element, Compound, or
Mixture?
Table Sugar
Element, Compound, or
Mixture?
Diamond
Aqueous Copper Sulfate
Chemical Names & Symbols
•Elements combine in specific ratios to form
compounds
Symbol for sulfur
Symbol for copper
Symbol for oxygen
Subscript for oxygen
Names and Symbols (cont.)
•The first letter of an element’s symbol is always
uppercase, and if there is a second letter it is
always lowercase.
•Compounds are represented by chemical
formulas.
•Chemical formula: A combination of symbols and
subscripts that indicates the number and types of
elements in a compound.
Examples of Element Symbols
Examples of Chemical Formulas for 2 different
compounds.
Copper Sulfate, CuSO4(s)
Copper sulfide, CuS(s)
Copper carbonate hydroxide
Cu2(CO3)(OH)2(s)
•Substances come in different physical forms,
called phases.
•Phase: The physical form a substance is in,
such as solid, liquid, or gas. Phase is greatly
influenced by temperature.
•Aqueous: A substance is aqueous when it is
dissolved in water.
• The symbols (s), (l), (g), and (aq) indicate the
physical form or phase of a substance and whether it
is dissolved in water.