Welcome to the world of BONDING!!!
Bonding
 Chemical Bonding is the joining of atoms to form ___________ and ___________
 Atoms bond to achieve a state of ___________ (stable outer shell of electrons)
 It is the transfer or sharing of ___________
 Bonding occurs during a chemical reaction and results in a chemical ___________ (example: Na+ and
Cl- ions react to give a molecule, NaCl)
Electronegativity
 A measure of the ___________ an atom has for bonding electrons
 ___________ is the most reactive non-metal, and therefore has the greatest attraction for the electron – it
is the most electronegative element
 On the periodic table, the general trend is that electronegativity ___________ going up a group and
right across a period
 The difference in electronegativites can help predict what type of bond will be formed
Types of Bonds
1. ___________
2. ___________
3. ___________
Ionic
 Occurs between a ___________and a nonmetal
 Occurs between two atoms with a ___________ difference in electronegativity (typically 1.7 or greater)
 Electrons are completely ___________, forming atoms with net positive and net negative charge
 Salts are often formed
 tend to have ___________ melting and boiling points
 can't melt them with a Bunsen burner
 very hard and very ___________
 ___________ electricity when they dissolve in water
Covalent
 generally have much ___________ melting and boiling points
 are soft and squishy (compared to ionic compounds)
 tend to be more ___________ than ionic compounds
 Due to H and C in a combustion reaction
 don't ___________ electricity in water
 aren't usually very ___________ in water
Metalic
 Occurs between atoms with ___________ electronegativity
 Occurs between atoms with 1, 2, or 3 valence electrons (many vacancies in shell)
 _______ ______ overlap, allowing electrons to become __________(move freely inside the structure)
 Positively charged nuclei and negatively charged electrons hold the metal together with strong forces of
attraction
Polarity
 when a molecule acts like a little ___________
 one side of the molecule has ___________ electrons than the other side
 Only ___________ bonds can be polar
 A polar covalent bond results when electrons are shared ___________ by nuclei
 One atom attracts the electrons more than the other atom
 The polarity of a bond depends on the difference of ___________
 This difference also helps to predict which type of bond will form.

The ___________ the difference the more ionic the bond will be.
Dipole Moment
 A dipole moment results when a ___________ molecule has a center for positive charge separate from a
center for negative charge
 The ___________ starts on the positive side and points to the ___________ side.
 All ___________ bonds have a dipole moment.
 The polarity of water affects its properties
 Permits ___________ compounds to dissolve in it
 Causes water to remain liquid at higher temperature
Can we rank the polarity? _______
Why does the formation of an ion cause the electron configuration to change to a noble gas?
BECAUSE IT’S STABLE!!! When representative metal and nonmetals react, they transfer ___________ in
such a way that both the _______ and the ________ have noble gas electron configurations. When nonmetals
react they share electrons in a way that leads to _______ atoms having noble gas electron configurations
Octet rule - every atom wants to have eight ___________ electrons, just like the nearest noble gas
Duet rule – ___________ only wants 2 valence electrons
*exception one* - boron (B) – it only needs 6 valence electrons.
*exception two* - _______ - it only needs ___ valence electrons.
Predicting Compounds
 Chemical compounds are always electrically ___________.
 That helps up figure out formulas.
 Ex. Li+ and F- => LiF
Size Does Matter
 When atoms ___________ or ___________ electrons their
relative size changes.
 Cations are s ___________ than parent atom
 Anions are ___________ than parent atom
Structure
 All the ___________ anions get packed closely together.
 Forms rows and columns
 ___________ cations fill in the small spaces.
 Still in the same rows and columns.
 Ions are packed together to ___________ the attractions
between ions
Lewis Structures!!!
Remember!!! Bonding involves only ___________ electrons of atoms. What are valence electrons?
 Lewis Dot Diagram and Lewis Structures are the same thing.
 Lewis Structures represent how the valence electrons are ___________
 Most important requirement
 Atoms achieve ___________ electron configuration (octet rule, duet rule)
 ___________ pairs are shared between 2 atoms
 Unshared pairs (___________) are not shared and not involved in bonding
Multiple Bonds
only covalent bonds
Single bond – 1 pair of electrons is shared by 2 atoms
Double bond – 2 pairs of electrons are shared by 2 atoms
Triple bond – 3 pairs of electrons are shared by 2 atoms
Steps for Writing Lewis Structures
1. Find the total # of valence electrons of all the atoms.
2. Use one pair to form a bond between each pair of bonded atoms
3. Arrange remaining electrons to satisfy duet rule and octet rule.
Try doing H2O
Let’s try 3 more:
•CCl4
•PH3
•CN- (this one is tricky)
Intramolecular forces vs. Intermolecular forces
 Intramolecular forces keep the atoms in a compound stuck to each other. (chemical bonds)
 Intermolecular forces hold two covalent molecules to one another
 aren't chemical bonds, instead, based on magnetic attractions between different molecules
 caused by polarity
Intermolecular Forces
 Three main types
1. Dipole-dipole forces
2. Hydrogen bonds
3. Van der Waals forces
Dipole-dipole forces
 Two molecules that both behave like little magnets stick to each other
 Strength depends on how polar the molecule is
 The larger the polarity the stronger the force
 The molecules of every polar compound are stuck to each other by these dipole-dipole forces.
Hydrogen bonds
 Occurs with polar molecules
 Lone pairs are attracted toward the partial-positively charged H atoms on nearby molecules
 Generally much stronger than dipole-dipole forces
 Van der Waals forces



Weakest of the three intermolecular forces.
When non-polar molecules stick together due to magnetic attractions.
always operate in any substance
Van der Waals forces
Now, I know what you're going to say: "Mr. B, only polar molecules behave like magnets. How can a
non-polar molecule have magnetic attractions? If a molecule is non-polar, where does the magnetic charge
come from? Furthermore, wouldn't this imply that nopolar molecules are really polar? What gives?"
These two molecules are both non-polar. The electric charge in each molecule is represented by the
color green. As you might imagine, the green color is evenly spread all over the molecule because none of the
atoms grab electrons more than any of the others. These molecules are happy.
Uh oh. There's a problem in happy molecule land. As you might remember, the electrons in atoms
jump around pretty much at random within a specific area. Unfortunately for the atom on the left, the electrons
have all jumped to the left of the molecule because of these random movements. This has caused the molecule
on the left to get a little bit of polarity, as shown by the red plus and minus signs.
Even more trouble is on the way. Because the molecule on the left became slightly polar, the
negatively-charged electrons in the molecule on the right all moved over so they could be next to the partial
positive charge on the molecule on the left. Because both molecules now have a little bit of polarity, they stick
to each other.
Fortunately, all is well in non-polar molecule-land. Because these polarities depended on random
electron motion, it goes away when the random electron motion makes the charges even out over the whole
molecule. For this reason, this is referred to as "temporarily induced dipoles", because the dipoles only last for
a very short time. Not only are these forces short-lived, but they're also very weak because they don't last for
very long.