Unit 4, Lesson 2
Ionic and Covalent Bonding
Why Do Chemical Bonds
Form?
• Generally, atoms join to form
bonds so that each atom has a
stable electron configuration.
Three basic ways that atoms bond:
1. Ionic Bonding
2. Covalent Bonding (molecular bonding)
3. Metallic Bonding
Ionic Bond
• Bonds that form from the attractions
between oppositely charged ions.
• Between a metal and a nonmetal
Covalent Bond
• Atoms joined by covalent bonds share
electrons.
• Atoms may share more than one pair of
electrons
• Between a nonmetal and a nonmetal
Polar Covalent Bond
• Atoms do not always share electrons equally.
The bigger atom will tug on the smaller atom.
Metallic Bond
• Bonding between metals
• Metals are flexible and conduct electric
current well because their atoms and
electrons can move freely throughout a
metal’s packed structure.
Polyatomic Atoms
• A polyatomic ion
acts as a single unit
in a compound, just
as ions that consist
of a single atom do.
Some names of polyatomic anions
relate to the oxygen content of
the anion
Determine if the following compounds
are likely to have ionic or covalent
bonds.
ionic
methanol, CH3OH
ionic
ozone, O3
strontium chloride, SrCl2
covalent
magnesium oxide, MgO
covalent
Draw the structural formula for
acetylene, C2H2.
• The atoms of acetylene bond in the order
HCCH. Carbon and hydrogen atoms share two
electrons, and each carbon atom must have a
total of four bonds. How many electrons do
the carbon atoms share?
Identify which two of the
following substances will conduct
electric current, and explain why.
• aluminum foil
Aluminum foil will conduct
electricity because it is a metal
and its valence electrons are free
to move.
• sugar, C12H22O11, dissolved in water
KOH dissolved in water will conduct
electricity because its ions are free to
move.
• potassium hydroxide, KOH, dissolved in water
Explain why electrons are shared
equally in oxygen, O2, but not in
carbon monoxide, CO.
Because the atoms in a molecule of oxygen
are the same, they attract and share
electrons equally.
Carbon and oxygen attract electrons
differently, so electron sharing is unequal.
Predict whether a silver coin can
conduct electricity. What kind of
bonds does silver have?
Silver has metallic bonds so it
has electrons that are free to
move. The coin will conduct
electricity.
Identify which of the bonds in
calcium hydroxide, Ca(OH)2, are
ionic and which are covalent.
The compound contains an Ca 2+ ion and 2OH- ions.
These ions are held together by ionic bonds.
OH- consists of covalently bonded oxygen and
hydrogen ions.
Does dinitrogen tetroxide, N2O4,
have covalent or ionic bonds?
Explain how you reached your
conclusion.
Dinitrogen tetroxide has covalent
bonds because both nitrogen and
oxygen are nonmetals.
An atom of the element iodine, I, has
much more attraction for electrons
than an atom of strontium, Sr, does.
What kind of bonds are likely to form
between atoms of the two elements?
Ionic bonds will form between
iodine and strontium
How are metallic bonds similar to
covalent bonds? How are they
different?
Metallic bonds are similar to covalent bonds
in that electrons are shared between atoms.
Metallic bonds are different from covalent
bonds in that electrons are free to move
around in the space between the atoms.