Test 7:
Chemical
Bonding
Cartoon courtesy of NearingZero.net
Basic Info
(Put these notes on page 1 of your Bonding Packet)
1. Chemical bonds are attractive forces
that hold atoms together.
2. Compounds – 2 or more different atoms
chemically bonded together
ex: NaCl or H2O
3. Diatomic Elements – 2 of the same
atoms bonded together
ex: H2 O2 F2 Br2 I2 N2 Cl2
(Put on page 1 of packet)
4. Electronegativity – an atom’s attraction
for electrons (Table S)
Metals – Low #’s
Nonmetals – Big #’s
Think
Metals lose e- & form + ions
Nonmetals gain e- & form - ions
Electronegativity
(attraction for another atom’s electrons)
Get
lost,
loser!
Hey! I
find your
electrons
attractive!
Chart to Memorize!
Type of
Bond
Ionic
Electronegativity
Difference…
>1.7
1.7>x>0
(equal to or more
than 1.7)
(less than 1.7 but
more than zero)
Transferred
Shared
unequally
2 Different
Nonmetals
H2O
Valence
Electrons are…
How to
Recognize…
Chemical Formula
for one example…
Metal &
Nonmetal
NaCl
(page 1)
Polar Nonpolar
Covalent Covalent
= zero
Shared
Equally
2 of the same
Nonmetals
H2
Electronegativity Chart
To Determine
Electronegativity
Difference for CaBr2:
Br = 3.0
Ca = 1.3
Difference is 1.7
So CaBr2 Bond is Ionic
Formation of Ionic Bond
Note: Electrons are transferred
NaCl
Crystal Lattice
The melting points of some Ionic
Compounds are as follows:
NaF
KCl
LiCl
993 oC
770 oC
605 oC
These high melting points are
experimental evidence that Ionic Bonds
are VERY STRONG. (Hard to break just
by heating).
Formation of Polar Covalent Bond
Note: Electrons are shared
Animation for Bonds
Chemical Bonding (page 2)
1. Octet Rule – Atoms want to have 8 valence
electrons (except H & He – need 2).
2. Forming Bonds – releases energy.
Mg + S  MgS + energy
(energy after  means its given off)
3. Breaking Bonds – requires energy.
MgS + energy  Mg + S
(energy before  means its needs or absorbed)
4. Ionic Bond – ED 1.7 or more
5. Polar Covalent Bond – ED greater than 0, but less than
1.7
6. Nonpolar Covalent Bond – ED = zero
7. Table S – to calculate ED
8. Metallic Bonds – sea of mobile e(this is a special type of bond that holds atoms of metals
together & accounts for a metal’s luster and ability to
conduct electricity)
Bond Wheel
Ionic
1.7 or
more
(page 3)
Polar
Covalent
less
E.D.
than 1.7
Nonpolar
Covalent
= zero
HW
• Do page 5 & 6
Nonpolar Molecules
• May have PC or NPC chemical bonds, but are
Nonpolar Molecules due to their symmetry.
• Examples:
H2 O2 F2
etc.
CH4 CCl4 CF4 etc.
CO2
Polar Molecules
• Polar Molecules have PC bonds and are
Asymmetrical.
• They have uneven e- distribution.
• They have a positive and negative end.
• Examples:
H2O NH3 HF HBr HCl CO
Intermolecular Forces
• Attraction between polar molecules
• Example
Hydrogen Bonding
• Extra strong IMF
• Found for H with NOF
• H2O NH3 HF