Stability in Bonding
Combined Elements
 Some of the matter around you is in the form of uncombined
elements such as copper, sulfur, and oxygen.
 When the conditions are right, these and other chemicals will
combine to form compounds.
 The green coating on the Statue of Liberty is an example of
these chemical changes. This new compound is copper
sulfate. (copper, sulfur, and oxygen combined)
 These new compounds have their own unique properties.
 Sodium chloride (table salt) is a compound made from
sodium (a shiny, soft, silver metal) and chlorine ( a poisonous
greenish-yellow gas).
Formulas
A chemical formula tells what elements a
compound contains and the exact number
of the atoms of each element in a unit of
the compound.
Example: NaCl stands for Sodium Chloride
and tells you that there is one atom of
sodium and one atom of chlorine in each
unit. H2O shows that there are two atoms of
hydrogen and one atom of oxygen in each
unit or molecule of water.
Some Familiar Compounds
Familiar Name
Chemical Name
Formula
Sand
Silicon dioxide
SiO2
Cane sugar
Sucrose
C12 H22 O11
Lime
Calcium oxide
CaO
Vinegar
Acetic acid
HC2H3O2
Stomach acid
Hydrochloric acid
HCl
Atomic Stability
Atoms combine when the compound
formed is more stable than the separate
atoms.
However, some of the atoms are stable by
themselves.
The Unique Noble Gases
 To understand the stability of the noble gases, you
must look at electron dot diagrams.
 Electron dot diagrams show only the electrons in
the outer energy level of an atom.
 Ex. Elements in Group 1 have one electron in the
outer energy level, Group 2 has two, Group 13 has
3, Group 14 has 4, and so on to Group 18 which
has 8.
 An atom is chemically stable when the outer
energy level is complete.
 The noble gases are stable because they each
have a complete outer energy level.
Energy Levels and Other Elements
 Groups 1, 2, 13, 14, 15, 16, and 17 do not have a
full outer energy level, so they are more stable
when they are found in compounds.
 For example, hydrogen only has one electron in its
outer energy level, which means its outer energy
level is not complete. This is why there are so
many hydrogen-containing compounds found on
earth.
Outer Energy LevelsGetting Their Fill
 Atoms with partially stable outer energy levels can
lose, gain, or share electrons to obtain a stable
outer energy level.
 They do this by combining with other elements that
have partially complete outer energy levels.
 This helps them both become stable.
 Example: sodium and chlorine
Stability is Reached
 Sodium has only one electron in its outer energy
level, which is lost to combine with chlorine in
sodium chloride.
 Now we look to next level down in sodium and see
that it is full, so now both elements have a
complete energy level and both are now stable.
 When atoms gain, lose, or share electrons, an
attraction forms between the atoms, pulling them
together to form a compound. This attraction is
called a chemical bond.
 A chemical bond is the force that holds atoms
together in a compound.