Chemical Bonding
and Formulas
Adapted from:
www.rsu.edu/faculty/mallen
Available online @:
www.redwood.org/stewart
# of p
2e-
Non-metals 3e- 4e- 5e- 6e- 7e-
2 e- (in 1st level when stable, full)
1e-
8 e-
# of p + n
(in 2nd level when stable, full)
Metals
8 e- (in 3rd level when stable (18 when full))
8e-
(exc
He)
8 e- (in 4th level when stable (32 when full))
8 e- (in 5th level when stable (50 when full))
8 e- (in 6th level when stable (72 when full))
98 e- in 7th level when full
Alkali
Metals
Alkali
Earth
Metals
Halogens
Noble
Periods Families/Groups
Gases
• I. Review: The periodic table of the elements.
II. Valence Electrons and Diagrams
(Review)
Chemical behavior is determined by the
outer electrons.
• These are called valence electrons
• Elements react so as to FILL
or EMPTY their outer shell
and become more STABLE.
• A full outer shell has 8 electrons except
elements H and He (since the 1st shell has only 2
electrons).
These outer shell electrons are represented
using electron dot diagrams.
• see next slide
Give up 1 to be empty
Need 2 to be full
Need 1 to be full
• Electron dot diagrams (showing valence electrons) for the
representative elements (electrons present in outer shell).
II. Valence Electrons and Diagrams (Review)
III. Types of
Chemical Bonds
metal
– IONIC BONDS:When an atom or
molecule gains or loses an electron it
forms an ionic bond (when a metal and
non-metal bond).
• A cation has lost an electron and
therefore has a positive charge.
These are the metals which always
tend to lose electrons. (FAMILIES
1,2,3)
• An anion has gained an electron
and therefore has a negative charge.
These are the nonmetals which
always tend to gain electrons.
(FAMILIES 5,6,7)
Na•
+
1 valence electron-unstable
Electron dot
diagam
Nonmetal
¨
[Na]:Cl:
¨
¨
•Cl:
¨
compound
or
Na:Cl:
7 valence
electrons--unstable
¨
Each
atom has 0 (empty) or 8
(full)
valence electrons & is
¨
Electron
dot diagam showing
how valence
electrons have been
transferred
Metal
Lithium (Li)
Li+
Li+ and F- will form an ionic bond
-
Li + F  LiF.
Non-Metal
+
Flourine (F)
F-
• (A) Metals lose their outer electrons to acquire a
noble gas structure and become positive ions. (B)
Nonmetals gain electrons to acquire an outer noble
gas structure and become negative ions.
III. Types of Chemical Bonds
Note that all atoms in
drawing are non-metals
–COVALENT BONDS:When
atoms share electrons a covalent
bond is formed (when 2 non-metals
bond).
:Ö:
+
:Ö:
6 valence
electrons--unstable 6 valence
electrons--Electron dot
unstable
diagam
:Ö :: Ö:
covalent
Each atom has 8
valence electrons and is
STABLE
or
:Ö : : Ö:
Electron dot diagram
showing how valence
electrons are shared
(with circles)
IV. Chemical Formulas
• Atoms form elements, compounds., and molecules.
Chemical formulas show the make-up of elements,
compounds, and molecules. Chemical formulas follow
these rules:
¨
• Electron dots are not included ( Na:Cl:¨ written as NaCl).
• Subscripts (example: H2) after symbols indicate the
number of that atom present (NaHCO3 has 3 oxygens)
When no subscript is present, that indicates that one
atom is present.
• If the subscript follows a parenthesis, all atoms within the
parenthesis are present in that amount (Mg(OH)2 has 2
oxygens).
• A coefficient in front of the element, compound, or
molecule (example: 3 OH) indicates there are multiple
molecules present (4CaCO3 has 12 oxygens).