Compounds and Bonding
Compounds
Compounds = contains two or more different
elements chemically bonded together
Most elements are in the form of a compound, very
rarely as a single element
Mixture = contains two or more elements or
compounds that ARE NOT bonded together
Common Compounds
Salt – NaCl (sodium + chlorine = sodium chloride)
Sugar – made up of Carbon, Hydrogen, and oxygen
Sucrose, glucose, fructose…
Properties of Compounds
Properties come more from the structure and
composition rather than the elements themselves
 Example: Aspirin – made up of oxygen, hydrogen and carbon. So is
formaldehyde and polyethlyene (plastic wrap). They even have the
same chemical formulas. The properties of aspirin as a pain reliever
come from the combination the shape and the bonds
Chemical Bonds
There are two types of chemical bonds:
1. Covalent Bonds: valence electrons are shared
between two or more elements
 NONMETALS
2. Ionic Bonds: valence electrons are transferred
from one element to another
 Metal and a Nonmetal
Bonds will be shown by lines or dots. Each line or
dot represents and electron
Chemical Formulas
 Identifies the number and element of each type of
atom in a compound.
 CH4
 H2 O
 CO2
Covalent Bonding
SHARED ELECTRONS
A group of covalently bonded compounds is
called a MOLECULE
Typically non-metals bonding to other gasses or
non-metals
Double and Triple Bonds – represent multiple
electrons
Ionic Bonding
When an electron is either lost or gained
(transferred)
ALMOST ALWAYS includes one metal (metals are
conductors – they will always LOSE their electron!)
One electron is transferred from a metal to a nonmetal
The bond is based on electrical attractiveness
 Positive attracting a negative
Ionic Bonding Cont’d
 When an element gains or loses an electron, it becomes an
ION
 For example: Salt!
 Sodium (Na) is a metal. When it bonds with Chlorine (Cl), Na
will lose its one valence electron.
 Na becomes a positively charged ion, because it lost an electron
 Cl becomes a negatively charged ion, because it gained an
electron
 Another example: MgCl2
 DOES NOT BECOME A MOLECULE! Ionic bonds are not
limited to one element each, because of the charges,
they will be attracted to all neighboring ions.
Hints to remember
 An element will bond with as many other elements as it has valence
electrons
 4 valence electrons means it can make 4 other bonds (wants to get to 8 and
be happy!)
 3 valence electrons means it can make 5 other bonds
 Covalent bonds are SHARED and form MOLECULES
 Typically non-metals bonding together in long, complex chains and
compounds
 IONIC bonds form IONS!!! Based on charges and gaining and losing
electrons
 Metals bonding with non-metals
Energy in Bonding
Free atoms contain a large amount of energy
This energy is lost when they bond to another
element
Energy is released when chemical bonds form
Some elements are more reactive (willing to form
bonds and compounds) then others.
The closer you are to the noble gasses, the more
reactive!
 Na is highly reactive (1 electron away) and so is Cl (1
electron away). But these elements in pure form
together create an explosion!