c ovalent c ompounds. 1. usually soft and squishy 2. not soluble in water 3. does not conduct...
TRANSCRIPT
COVALENT COMPOUNDS
COVALENT COMPOUNDS1. Usually soft and squishy
2. Not soluble in water
3. Does not conduct electricity
4. Low melting points
5. Low boiling points
TWO TYPES OF BONDS Ionic: Electrons are transferred
Covalent: Electrons are shared Non-polar covalent: equally shared
Polar Covalent: unevenly shared
NAMING COVALENT COMPOUNDS
NAMING COMPOUNDS
Nonmetal – Nonmetal
USE PREFIXES!
1. Change the ending of the second word to -ide
2. No mono on the first word
3. Drop any double vowels
COVALENT PREFIXESNumber of Atoms Prefix
1 Mono-2 Di-3 Tri-4 Tetra-5 Penta-6 Hexa-7 Hepta-8 Octa-9 Nona-
10 Deca-
THE PREFIX TELLS YOU HOW MANY ATOMS YOU
HAVE!NO CRISS CROSS!!!!
EXAMPLES
1. CO
2. CO2
3. SO2
4. SO3
5. N2H4
6. N2O3
1. Carbon Monoxide
2. Carbon Dioxide
3. Sulfur Dioxide
4. Sulfur Trioxide
5. Dinitrogen Tetrahydride
6. Dinitrogen Trioxide
EXAMPLES
1. disilicon hexafluoride
2. tricarbon octachloride
3. phosphorus pentabromide
4. nitrogen monoxide
5. selenium difluoride
6. dihydrogen monoxide
1. Si2F6
2. C2Cl8
3. PBr5
4. NO
5. SeF2
6. H2O
EMPIRICAL AND MOLECULAR FORMULAS
Define Empirical Formula:A chemical formula that gives the simplest whole-number ratio of the elements in the formula.
Which of the following is an empirical formula? CO2 C2O4
Fe2Cl6 FeCl3
Define Molecular Formula:A chemical formula that gives the actual number of the elements in the molecular compound. For the following molecular formulas, write the empirical formula:
Molecular: Empirical: C2H4 C6H12O6
C9H21O6N3
LEWIS STRUCTURES
F F
LEWIS STRUCTURES FOR COMPOUNDS The pair of dots between two symbols
represents the shared pair. How many shared pairs does each fluorine have
below?
An unshared pair, also called a lone pair, is a pair of electrons that is not involved in bonding and that belongs exclusively to one atom.
F F
LEWIS STRUCTURES
The shared pair of electrons is often replaced by a long dash.
Each dash represents TWO electrons
F F+
7e- 7e-
F F
8e- 8e-
F F
F F
Lewis structure of F2
lone pairslone pairs
lone pairslone pairs
single covalent bond
single covalent bond
WHY SHOULD TWO ATOMS SHARE ELECTRONS?
To get a valence of 8 electrons!
HC
HCH
H
MULTIPLE COVALENT BONDS double bond:
covalent bond in which two pairs of electrons are shared between two atoms
shown by two side-by-side pairs of dots or by two parallel dashes
MULTIPLE COVALENT BONDS triple bond:
covalent bond in which three pairs of electrons are shared between two atoms
shown by three side-by-side pairs of dots or by three parallel dashes
STEPS FOR DRAWING LEWIS STRUCTURES1. Draw the Lewis Dot diagram for each individual
atom
2. Count up the number of valence electrons
3. Connect the atoms together to pair up the electrons (put atoms that can make the most connections in the center)
4. Once all electrons are paired, recount electrons to double check total valence
PRACTICE
Draw the Lewis Structure for HBr
1. H Br2. 1 + 7 = 8
3. H — Br
4. 2 + 6 = 8
BOND POLARITY
Which element is the most electronegative?
H F
Fluorine- Has 7 valence e- and wants 8
ability of an atom to attract electrons
REVIEW:WHAT IS ELECTRONEGATIVITY?
H F FH
electron richregion
electron poorregion
e- riche- poor
d+ d-
POLAR BOND :
covalent bond with greater electron density around one of the two atoms
1
2
3 4 5 6 7 8 9 10 11 12
13 14 15 16 17
18
NonpolarCovalentshare e-
Polar Covalentpartial transfer of e-
Ionictransfer e-
Increasing difference in electronegativity
Electronegativity Difference Bond Type
0 to 0.3 Nonpolar Covalent
0.4 to 1.6 Polar Covalent
1.7 Ionic
WHAT TYPE OF BOND IS IT?
Classify the following bonds as ionic, polar covalent,or covalent:
Cs – 0.7 Cl – 3.0 3.0 – 0.7 = 2.3 Ionic
H – 2.1 S – 2.5 2.5 – 2.1 = 0.4 Polar Covalent
Cl – 3.0 N – 3.0 3.0 – 3.0 = 0 Nonpolar Covalent
Cs to Cl
H to S
Cl to N
INTERMOLECULAR FORCES
Intermolecular forces: attractive forces between molecules.
Intramolecular forces: attractive forces within a molecule (the bonds)
intramolecular forces are much stronger than intermolecular forces
Intramolecular Forces
Intramolecular Forces
Intermolecular Forces
DIPOLES
What is a dipole?
A polar molecule
Uneven sharing of electrons so there is a separation of charge
DIPOLE-DIPOLE FORCES
Attraction between two polar molecules
— + — +
HYDROGEN BONDING
Special type of Dipole – Dipole
Attraction between:Hydrogen and Nitrogen/Oxygen/Fluorine
DIPOLE – INDUCED DIPOLE Attraction between one polar and one
nonpolar molecule
— +
— + — +
Electrons shift toward
positive end of dipole
LONDON DISPERSION FORCES Attraction between two nonpolar molecules
— + — +
Electrons become
uneven and form a dipole
STRENGTH OF IMF
Hydrogen Bond
Dipole – Dipole
Dipole – Induced Dipole
London Dispersion Forces
strongest
weakest
WHAT DOES IMF EFFECT? Viscosity
Surface Tension
Cohesion/Adhesion
Boiling Point
Stronger IMF Higher Viscosity
VISCOSITY
Measures a fluid’s resistance to flow
Stronger IMF Higher Surface Tension
SURFACE TENSION
result of an imbalance of forces at the surface of a liquid.
Adhesion
Cohesion
ADHESION AND COHESION Cohesion:
intermolecular attraction between like molecules Adhesion:
intermolecular attraction between unlike molecules
BOILING POINT
Point at which liquid particles escape the surface of the liquid into the gas phase
Stronger IMF Higher Boiling Point