A. Electronegativity - The ability of an atom to attract electrons to itself in a bond
1. Periodic Trends (link to size)Metals – Low ElectronegativityNon- Metals – High Electroneg
The smaller the atom, the higher the electronegativity
Types of Bonds
a. Molecular Compounds (non-metals)• Sharing of electrons• Covalent or polar covalent bonds• Ex: H2
b. Ionic Compounds (metal + non-metal)• Exchange (stealing) of electrons• Ex: NaCl
Types of Bonds
3. Types of bondsElectronegatvity Difference
Example: Na-F
Types of Bonds
Are the following bonds ionic, polar covalent or covalent?
Ba – Br C – NBe – F B – HO – H Be – ClP – H C – HO – O
Types of Bonds
Ionic – Electron is completely removed from one atom and goes to another
a. Metal – Low e-neg (loses e-)b. Non-metal – high e-neg (gains e-)
Ionic
IA IIA IIIA IVA VA VIA VIIA
HydrideH-
LithiumLi+
BerylliumBe2+
CarbideC4-
NitrideN3-
OxideO2-
FluorideF-
SodiumNa+
MagnesiumMg2+
AluminumAl3+
PhosphideP3-
SulfideS2-
ChlorideCl-
PotassiumK+
CalciumCa2+
SelenideSe2-
BromideBr-
RubidiumRb+
StrontiumSr2+
TellurideTe2-
IodideI-
CesiumCs+
BariumBa2+
Common Charges
Complete the following chart:Formula Lewis Dot
K and I
Sr and F
Ba and Cl
Sr and N
Ba and O
Complete the following chart:Formula Lewis Dot
K and S
Al and O
Na and Br
Ca and O
1. Not Separate molecules2. Crystal Lattice – Regular 3D pattern in an
ionic solid
Ionic Solids
Ionic Solids
at lattice points ions at lattice points
1. Water (molecule) dissolves salt (ionic crystal):
Ions in Water
Molecules
Many ionic compounds are called salts
CaCl2 Calcium Chloride (Quik-Joe)NaHCO3 Sodium bicarbonate(Baking soda)NaF Sodium Fluoride (toothpaste)CaCO3 Calcium Carbonate(Chalk, antacid)NaOH Sodium Hydroxide (Drano)MgSO4 Magnesium Sulfate(Epsom Salts)
All big clumps (crystals) of Ions
Other Salts
• Group of atoms held together by covalent and polar covalent bonds (SHARING)
• Usually composed of non-metals • Stronger than Ionic bonds• Separate (discrete) groups of
atoms
What is a Molecule?
A. Single Bonds (LD and Stick)CH4
H2O
(bonded versus lone pairs)
Old School Lewis Dots
The Lone Pear(Pair) rides again!
N and HP and FCl and ONH2CH3
Old School Lewis Dots
You try:As and HN and BrCH3CH2OH
NH2CH2SiCl3
CH3OCH3
Old School Lewis Dots
As and ClC and BrCH3CH2NH2
CH3OCH2CH3
B. Multiple BondsCO2
C2H2
Old School Lewis Dots
You Try:HCNN2
AlN
O2
Old School Lewis Dots
Rules1. Sum all valence electrons, including
charges2. Single Bonds3. Outer atoms get an octet except H4. Center gets rest even if it violates the octet5. Double/triple bonds if center atom still
does not have an octet
Lewis Dots
NH3
NCl3
SF6
Br2O
ClF5
Lewis Dots
You try:SF4
KrF4
Cl2O
ClF3
H2SO4
Warm-Up:
CH3CH2NH2
SeF4
KrCl4
H2O2
BaCl2 (this is an ionic cmpd)
CO2
HCNCN-
ICl4-
NO+
Lewis Dots
CO32-
H3O+
NH4+
PO43-
SO2
• Hydrogenonly makes one bond• Gr I, II and III• Especially if with a halogen
BeCl2 BCl3 AlCl3
Less Than an Octet
• Non-Metals starting with P
More Than an Octet
P S Cl Ar
As Se Br Kr
Te I Xe
PCl5
Warm-Up: O3
Definition – When a molecule can exist in more than one arrangement of electrons1. Atoms don’t move2. Only the electrons (double bonds) move3. Also called “delocalized bonding”
Resonance Structures
Si2H4
AsO43-
CS32-
H3S+
PH4+
SPECIAL NOTE:
Oxygen rarely makes three bonds for resonance structures. Those structures are not common.
Resonance Structures
PO3-
HSO3+
Examples1. NO2
-, CO32-, CHO2
-, HNO3
2. Which needs resonance, SO3 or
SO32-
Resonance Structures
• Valence Shell Electron Pair Repulsion Theory (VSEPR)
• VSEPR – Valence electron pairs on the central atom push as far apart as possible.
Shapes of Molecules
1. Linear (180o)BeH2 CO2
Shapes of Molecules
Shapes of Molecules
2. Trigonal Planar (120o)NO3
-
Shapes of Molecules
Shapes of Molecules
3. Tetrahedral (109.5o)CH4
Shapes of Molecules
Shapes of Molecules
4. Trigonal Pyramidal (~107o)NH3
Shapes of Molecules
Shapes of Molecules
5. Bent (Type I, ~104.5o)H2O
Shapes of Molecules
Shapes of Molecules
Shapes of Molecules
OH H
Shapes of Molecules
Bent (Type II, 120o)SO2
•Atoms are bent•Bond angle = 120o
6. Trigonal Bipyramid (120o, 90o)PCl5
Shapes of Molecules
Shapes of Molecules
7. Octahedral (90o)SF6
Shapes of Molecules
Shapes of Molecules
DRAW LEWIS DOT STRUCTURES AND PREDICT THE BOND ANGLES FOR:
PH3 GeO2
PCl5 NCl3
H2S SiH4
CF4 SO32-
SeCl6 SO3
Ex: All single bonds:PH3 H2S SiH4
SeCl6 AsF5 BeCl2
CH3F HF BF3
Shapes of Molecules
Ex: Multiple Bonds:N2
HCNCO2
H2CO
Shapes of Molecules
SO22+ SO2
2- SO2
SO3 SF6
Shapes of Molecules
1. Examples:BeH2
H2O
BH3
NH3
2. There is no relationship between formula and shape
Shapes and Formula?
PO2- PO3
- PO33-
PO43- XeF4
Household Molecules H2O
HClNH3
H2SO4
1. Polar molecule – Overall, the electrons are attracted more to one end of an entire molecule
2. Non-Polar Molecule – The electrons are spread out evenly over the entire molecule
-/ + Partial (not full) charges
Polar Molecules
H2 H2O
CH4 H2CO (C is the center)
H2 H2O
CH4 H2CO
BeCl2
NH3
CO2
CSO
HCN (triple bond)
CCl4 CH3ClCH2Cl2
CHCl3
HBeClHBr
CH3Cl CH2Cl2
CHCl3 HBeCl HBr
Polar Molecules
Lewis Dot Shape Polar or Non-polar molecule?
H2O
NH3
CH3Cl
CH3CH2OH
SO2
Hydrogen Bondinga. Water Beadingb. SurfaceTensionc. Iced. DNAe. Miscibility (NH3, ethanol)f. Immiscibility (Water and Oil)
Water Beading
Surface Tension
Surface Tension
Ice
Ice
MoleculesBoiling Point• Generally
increases with increasing molar mass
• H2O unusually high - H-bonding
DNA
DNA
DNA is TWO molecules
that are hydrogen
bonded (like a zipper)
DNA
Human Genome Project
• DNA in one cell = 1 meter• DNA in all your cells = 93,000,000 miles
Miscibility
•“Like dissolves like.”
•Polar dissolves Polar
•Water, ammonia
Miscibility
Miscibility
Miscibility
Miscibility
Miscibility
•Water, alcohol
•Water, alcohol
•Water, alcohol
Miscibility
•Water, alcohol
Miscibility
•Non-Polar dissolves Non-Polar
•oil paint, thinner
Miscibility
Would acetone (shown below) dissolve in water?
Acetone
:O: ||CH3CCH3
MoleculesLondon Dispersion Forces
• Very weak force• Caused by temporary imbalances in electrons
MoleculesLondon Forces: Inorganic Molecules• More electrons, more chance for temporary
dipole
Boiling Point TableHalogen Molar
MassBP(oC) Noble
GasAtomic Mass
BP(oC)
F2 (g) 38.0 -188 He 4.0 -268
Cl2 (g) 71.0 -35 Ne 20.2 -246
Br2 (l) 159.8 59 Ar 39.9 -186
I2 (s) 253.8 185 Kr 83.8 -152
Consider the following molecules:
Te2 S2 O2 Se2
a. Rank them from weakest to strongest London forces
b.Which should have the highest boiling point? Which should have the lowest?
c. Would it take more energy to melt a sample of carbon or silicon?
MoleculesLondon Forces: Organic Compounds• The longer the carbon chain, the higher the
London Dispersion Forces (the higher the melting point and boiling point)
BP(oC)CH4 -161.6C2H6 -88.63C3H8 -42.07C4H10 -0.5
Which should have a higher boiling point:
C6H14 or C12H26
Using you knowledge of “like dissolves like”, explain the following trends in solubility.
Alcohol Solubility in H2O (mol/100 g H2O at 20oC)
CH3OH ∞
CH3CH2OH ∞
CH3CH2CH2OH ∞
CH3CH2CH2CH2OH 0.11
CH3CH2CH2CH2CH2OH 0.030
CH3CH2CH2CH2CH2CH2OH 0.0058
CH3CH2CH2CH2CH2CH2CH2OH 0.0008
Explain the following trends in solubility in water
Emulsifying agents– Mayonaise– Soap
The Key to the Universe
You Try:
CCl4 NO3-
CH3Cl H2COCH2Cl2 H2S
Polar Molecules
KrCl4 Si2H4
BN CH3SiH2PH2
SiS2 H2SO4
OH O S O H
O
9. (c) Sc2+ (d) I2- (e) As2- 15. Rb+ Ba2+ Te2- N3-
16. Al3+, Mg2+, Na+, F-, O2-, N3-
20.RbF Rb2Te Rb3P
MgF2 MgTe Mg3P2
CrF3 Cr2Te3 CrP
22. BeS Cs2S Ga2S3 SrS
24.a) Ir8+ b) Sc3+ c) Pt6+ d) Co3+
e) Tc3+ f) Ag+
27. a) HI b) SeBr2 c) SiBr4 d) H3As
49. a) PC b) Cov c) PC d) Ionic
50. a) PC b) PC d) Ionic d) PC52. a) N-H b) Si-O c) S-F P-Cl
54.a) trigonal planar b) trigonal pyramidc) linear d) trigonal planare) trigonal planar
56.a) H2O c) NH4+
a) octahedral h) tetrahedralb) tetrahedral i) trigonal bipyramidc) linear j) trigonal pyramidd) trigonal planar k) octahedrale) bent l) linearf) trigonal planar m) linearg) Linear n) linear
Assessing the Objectives (page 278)a)2, 3b)Less than 109.5o
c) Trigonal Planard)Bente)Linear, 180o bent, 120o
Questions1. Rank the three liquids from weakest to the
strongest forces between their molecules.2.Discuss how you chose your rankings from the
results of the experiment.3.Is isopropyl alcohol or hexane more like
water? Explain, using the results from the experiments.
4.What information did the salt experiment provide about the molecules?
GAK – NEATNESS!!!!!!!1.Glue2.Food coloring3.Borax solution
Formula Lewis Dot
Ca and O
Ca and Br
P and H
C and F
N and F
Consider the following three chemical bonds:
C-O Cl-Br Rb-Cla. Determine the type of bond present in each
situationb.In which bond is an electron transferred?c. Draw the Lewis Dot structure of this ionic
compound.d.In which bond are electrons unequally
shared?e. Identify the element in that bond that the
electron spends more time with.
The element chlorine forms compounds with both strontium and sulfur.
a. Write the formula of the compound that forms between strontium and chlorine.
b. Draw the Lewis Dot Structure of this compound, indicating whether it is ionic or molecular.
c. Write the formula of the compound that forms between sulfur and chlorine.
d. Draw the Lewis Dot Structure of this compound, indicating whether it is ionic or molecular.
e. Is the structure you drew in (d) linear? Why or why not?
f. State the bond angle of the structure in (d).
Draw the Lewis Dot Structure and predict whether it is a polar or non-polar molecule
H2O
CH3CH(OH)CH3
CH3CH2CH2CH2CH2CH3
Water Isopropyl HexaneAlcohol
Draw Lewis Structures (Ionic)
BaF2 Li2O
Draw Lewis Structures (Molecular)
ClF3 SiO32- SO2
Compound Central Atom
BeH2 Tan
BH3 Tan
CH4, NH3, H2O Black
PCl5 Tan
SF6 Yellow or silver
7a. Octahedral h. Tetrahedral
b.Tetrahedral i. Trigonal bipyramid
c. Linear j. Trigonal pyramid
d.Trigonal Planar k. Octahedral
e. Bent I l. Linear
f. Trigonal Planar m. Linear
g.Linear n. Linear
1. Covalent, Ionic or Polar Covalent Bonds?
a. Ionic
b.Covalent
c. Polar Covalent
d.Ionic
e. Ionic
f. Polar Covalent
g.Polar Covalent
h.Ionic
3a. K+ Br-
b.Al3+ 3Cl-
c. 2Ga3+ 3O2-
d.2Li+ O2-
e. Ca2+ 2Br-
f. Na+ OH-
g.Ca2+ 2NO3-
h.2Na+ CO32-
i. 2Fe3+ 3SO42-
j. Co4+ 4NO2-
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