CHEMICAL BONDING
• COVALENT BONDS
• IONIC BONDS
• METALLIC BONDS
Reflection (pg 62)
• What is a metallic bond?
• Compare/contrast it to ionic/covalent bond
Metallic Bonds
• How atoms are held together in
the solid.
• Metals hold onto there valence
electrons very weakly.
• Think of them as positive ions
floating in a sea of electrons.
Sea of Electrons
• Electrons are free to move through the
solid.
• Metals conduct electricity.
+
+ + +
+ + + +
+ + + +
Characteristic of Metallic Bonds
• High electrical and thermal
conductivity
• Malleable, ductile, high
luster.
• Great amount of heat needed
to break these bonds.
IONIC BONDING
When an atom of a nonmetal
takes one or more electrons
from an atom of a metal
so both atoms end up with
eight valence electrons
IONIC BONDING
IS THE COMPOUND
AN IONIC COMPOUND?
METAL
NONMETAL
SUBSCRIPTS
IONIC BOND FORMATION
IONIC BONDING
ION – any atom with more or
less electrons that it is
supposed to have*
*Remember that the number of electrons
is supposed to be equal to the number of
Protons if the atom has a neutral charge
IONIC BONDING
Metals will tend to lose electrons
and become
POSITIVE CATIONS
Normal sodium atom
loses one electron
to become sodium ion
IONIC BONDING
+1
Na is
called a sodium ion
The +1 symbol means it
has lost one electron
IONIC BONDING
Nonmetals will tend to gain
electrons and become
NEGATIVE ANIONS
Normal chlorine atom
gains an electron
to become a chloride ion
IONIC BONDING
Cl-1 is called a chloride ion
The -1 symbol means it
has gained one electron
Properties of Ionic Compounds
• Hard, brittle solids.
• Strongest bond.
• Most dissolve in water
• Conduct electricity when
dissolved in water.
• High melting/ boiling pointsbecause of strong forces between
ions.
Crystalline structure
The
POSITIVE
CATIONS
stick to the
NEGATIVE
ANIONS, like
a magnet.
+
+
- - +
+ + - + - +
- + - +
COVALENT BOND
FORMATION
When one nonmetal shares one or
more electrons with an atom of
another nonmetal so both atoms end
up with eight valence electrons
COVALENT BONDING
IS THE COMPOUND
A COVALENT COMPOUND?
NONMETAL
NONMETAL
YES since it is made of only nonmetal elements
Polar Bonds
• When two different atoms are connected,
the atoms may not be shared equally.
• This is a polar covalent bond.
pages.uoregon.edu
Nonpolar Bonds
• When the atoms in a bond are the same, the
electrons are shared equally.
• This is a nonpolar covalent bond.
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Characteristics of Covalent Bonds
• Represented by Lewis structures
• Strong bond but weaker than Ionic
bonds
• Low melting points & boiling points
• Most do not dissolve in water
• Do not conduct electricity.
• Usually in a gas state at room
temperature
Covalent bonds
• Monatomic: contains one atom
• Diatomic: contains two atoms
BrINClHOF
Bromine (Br2), Iodine (I2), Nitrogen (N2), Chlorine
(Cl2), Hydrogen (H2), Oxygen (O2), Fluorine (F2)
You must have these memorized!!!!
• Polyatomic: contains more than one atom.
Octet Rule
• Octet rule: atoms tend to gain, lose, or share
electrons until they are surrounded by 8 valence
electrons (4 electron pairs).
• Exceptions:
• Hydrogen forms bonds in which it is surrounded
by only two electrons.
• Boron tends to form bonds in which it is
surrounded by 6 electrons.
• Main group elements in period 3 and up can form
bonds with expanded valance shells.
Lewis structure rules
• 1.Write the element symbol. Around this
draw dots—one for each valence electron.
• 2. The dots sould be spread over four sides.
Dots are not paired until all sides have at
least one dot.
• 3. It does not matter on which side dots are
placed. Example- Hydrogen can be drawn
in four ways:
Lewis structure rules
• 4. The number of valence electrons is equal
to the group number for groups 1 and 2. In
groups 13 to 18, subtract 10 and that is the
number of valence electrons.
Multiple bonds in Lewis
Structures
• Molecules containing carbon (C), nitrogen
(N), and oxygen (O) may form multiple
bonds.
• The need for multiple bonds becomes
obvious if there are not enough valence
electrons to complete octets by adding
unshared electron pairs.
Double bonds
• Produced by sharing two pairs of electrons
between two atoms.
Triple Bonds
• Produced by sharing three pairs of electrons
between two atoms.
MOLECULAR
SHAPES
OF
COVALENT
COMPOUNDS
VSepR tHEORY
What Vsepr means
Since electrons do not like each
other, because of their negative
charges, they orient themselves
as far apart as possible, from
each other.
This leads to molecules having
specific shapes.
Things to
remember
•Atoms bond to form an Octet
(8 outer electrons/full outer
energy level)
•Do NOT forget all electron
pairs, including unshared
electron pairs!!!
Linear
EXAMPLE:
BeF2
•The central atom is represented by A and the
atoms bonded to the central atom are B.
•The molecule AB2 is linear
•Bond Angle = 180°
Trigonal Planar
EXAMPLE:
GaF3
•The molecule AB3 makes an equilateral
triangle.
•Bond Angle = 120°
Tetrahedral
EXAMPLE:
CH4
•The molecule AB4 makes the shape of a
tetrahedral (kind of looks like a pyramid).
•Bond Angle = 109.5°