Chapter 6 Sections 6.1 – 6.4. 6.1 – Chemical Bonds Chemical Bond = A link between atoms Why does...
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Transcript of Chapter 6 Sections 6.1 – 6.4. 6.1 – Chemical Bonds Chemical Bond = A link between atoms Why does...
Chapter 6
Sections 6.1 – 6.4
6.1 – Chemical Bonds
Chemical Bond = A link between atoms
Why does it occur?
The nucleus of one atom is attracted to the electrons of another.
Types of Bonds (an overview)(You will see all of these again later in the chapter!)
1. Ionic BondIon = Atom which has gained or lost
electron(s)Metal =
-LEFT side of Periodic Table-Weak nucleus / Low Electronegativity-LOSERS of electrons-Become + charged ions
Types of Bonds (an overview)
1. Ionic Bond
Nonmetal =
-RIGHT side of Periodic Table
-Strong nucleus / High Electronegativity
-GRABBERS of electrons
-Become - charged ions
Types of Bonds1. Ionic Bonds
Atoms gain or lose valence electrons to become a NOBLE GAS CONFIGURATION
Examples:
Na =
Na ION =
Cl =
Cl ION =
Types of Bonds
1. Ionic Bonds
Ionic bond = A chemical bond between a cation (+) and an anion (-). Caused by a TRANSFER of electron(s).
Usually a metal + a nonmetal
Types of Bonds (an overview)(You will see all of these again later in the chapter!)
2. Covalent Bond = A bond caused by a SHARING of electrons
Usually a nonmetal + a nonmetal
Nonpolar Covalent = Equal sharing of the electrons. Atoms are close in strength
Polar Covalent = Unequal sharing of the electrons. One atom is a little bit stronger than the other World of Chemistry; #8
Chemical Bonds; End at 16:25 – formation of Hydrogen molecule
Types of BondsHow do you tell which type of bond it is?
-By ELECTRONEGATIVITY
A chart of electronegativity will be provided to you:
-The greater the difference in electronegativity – the more ionic the bond.
-Electrons spend more time closer to the element with higher electronegativity.
Types of BondsIf the ABSOLUTE VALUE of the electronegativity
difference is:
GREATER THAN 1.7 = IONIC Bond
LESS THAN 0.3 = NONPOLAR COVALENT Bond
0.3 – 1.7 = POLAR COVALENT Bond
Examples:
Types of Bonds (an overview)
3. Metallic bond
Usually metals only
-The metal gives up valence electrons.
-Electrons are free to move about.Atom
Electron Sea
More Detail on the Bond Types6.2 – Covalent Bonds
Covalent Bond = A sharing of electronsMolecule = A group of atoms held by
covalent bonds (ex – water)Diatomic Molecule = Molecule with only 2
atomsMolecular Compound = Compound made of
moleculesMolecular Formula = The type and number
of atoms in a molecule (ex – H2O)
Formation of Covalent Bonds
Sharing electrons in a covalent bond makes the atoms more stable and decreases the energy of the atoms. Energy is released when a bond is FORMED.
Overlapping of Orbitals – Example H2:
H H
+
H2
The Octet Rule
Atoms in a compound obtain the electron configuration of a NOBLE GAS to gain stability
Drawing Lewis Structures
-A picture of the covalent bonds in a molecule
-Connect valence electrons with LINES
-For Academic classes, atoms follow the octet rule unless stated
Examples:
Single Bond = 1 pair of electrons (2 e-s total) shared between two atoms
Double Bond = 2 pairs of electrons (4 total e-s) shared between two atoms
Triple Bond = 3 pairs of electrons (6 total e-s) shared between two atoms
*Single bonds are the LONGEST in length; Triple are the SHORTEST
*Single bonds have the LOWEST bond energy; Triple have the HIGHEST
Ionic Bond = Bond formed by the attraction of a cation (lost electrons) to an anion (gained electrons)
Crystal Lattice = 3-Dimensional network of ions
Formula Unit = Simplest ratio of ions
More Detail on the Bond Types6.3 – Ionic Bonds
NaCl
Dot structures for Ionic Compounds:
-Will reach noble gas configuration
-Draw an ARROW to show the transfer of e-
-Draw as many of each ion as needed
Examples:
Comparison of Ionic and Molecular
Molecular Compounds IONIC Compounds
Bond Type Covalent Bonds Ionic
Structure Individual Molecules
Crystal Lattice
Strength of Bond
Strong Bonds Very Strong Bonds
mp/bp Low mp / bp High mp / bp
Drawing Connect Dots Arrows with Charges
Other Conduct electricity when melted or in water
Drawing the Pictures – when you’re not told the TYPE of substance
• Do electronegativity difference first!!
• Examples:
6. 4- Metallic Bonding
Metals have LOW electronegativity – Will LOSE electrons
The steps:
-Donate valence electrons to electron sea
-Electrons free to move about
-All electrons in sea are shared by all atoms
6.4 – Metallic BondingProperties of Metals:1. Good conductors of heat – e- sea shakes
2. Good conductors of electricity – e- in sea can move
3. Malleable – atoms can be pushed closer
4. Ductile – atoms can be pushed closer
5. Luster – light bounces off e- sea
Chapter 6
Section 6.5
Putting Partial Charges on Molecules
Properties of MOLECULAR Compounds
VSEPR = Valence Shell Electron Pair Repulsion Theory
Valence electrons move as far away from each other as possible
1. Draw Lewis Structure2. Look at Central Atom3. Count electron areas (bonds + lone pairs)4. Use chart info
*Academic will be given a WORD BANK and the option to use Model Kits*
VSEPRAreas Bonds Lone
pairsShape Bond
AnglesStructure Example
2 2 0 Linear 180o http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php
BeCl2;CO2
3 3 0 Trigonal Planar 120o http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php
BF3
3 2 1 Bent <120o http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php
SO2
4 4 0 Tetrahedral 109.5o http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php
CH4
4 3 1 TrigonalPyramidal
<109.5o http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php
NH3
4 2 2 Bent <109.5o http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php
H2O
VSEPR
Examples:
VSEPR
Examples:
VSEPR
Examples:
Hybridization
Combination of equal energy orbitals to form new orbitals which all have the same shape and energy
Carbon:
C
BECOMES
C
1s22s22p2 four sp3 hybrid
Types of Molecules
FIRST – Draw Lewis Structure & Include Partial Charges!
1. Dipole = Molecule with overall charge
2. NonPolar With Polar Sites = Molecules with area of charge which cancel out
3. Nonpolar = Molecule with no areas of charge
Types of Molecules
How do you tell the difference?-Ask yourself these questions…
1. Is there charge on the molecule?
Yes2. Can it be sliced?
YES = Dipole NO = NPWPS
No = Nonpolar
Examples
Intermolecular ForcesAKA – EXTERNAL BONDS
The attraction BETWEEN Molecules
Types of External Bonds:
1. Dipole-Dipole Interactions
-Occur due to attraction between partial charges
-Occur between two dipoles (Fix notes) – the strongest external bond
Hydrogen Bond = External bond that involves a hydrogen atom
Intermolecular Forces2. London Force
-Occurs between Nonpolar (or Nonpolar With Polar Sites) molecules – CHANGE THIS IN THE NOTES!!
-Very weak connection (nonpolar to nonpolar is the weakest)
The Steps: (only needed for Honors)
A. Electrons in one molecule shift instantaneously to one side
B. Instantaneous charge results
C. Electrons in another molecule are repelled
D. Very weak attraction results
Properties Based on Number / Strength of External Bonds
1. State of Matters>l>g
2. Evaporation (*volatility)slow>fast
3. Thickness (*viscosity)thick>thin
4. Wetness (*adhesion)To feel wet the substance must bond to your skin (to the Na+Cl-)
5. DissolvingLIKE DISSOLVES LIKE
Demonstrations