6-1 Introduction to Chem Bonding

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6-1 Introduction to Chem Bonding

• a link between atoms that results from the
  mutual attraction of their nuclei for e-

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-Types of chem bonds

• 1. Ionic bond
• transfer of e-
• 2. Covalent bond
• sharing of e-s
• -bonds between unlike atoms are never completely
  ionic and rarely completely covalent.(Pauling)
• 3. Metallic bonds between metals

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• nonpolar-covalent bond
• cov bond which the bonding e-s are shared
  equally by the bonded atoms
• -resulting in a balanced
• distribution of elect charge

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• Polar
• meaning that they have an uneven distribution of
  charge
• Polar-cov bond
• the united atoms have an unequal attraction for
  the shared e-s

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-Why chem bonding occurs

• -if their PE is lowered by the change, two atoms
  will form a chem bond.

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6-2 Covalent Bonding and Molecular Compounds

• Molecule
• smallest unit quantity of matter which can exist
  by itself and retains all the prop of the
  original substances
• Diatomic molecule
• 2 like atom

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• Molecular cmpnd
• chem cmpnd whose simplest units are molecules
• Chem formula
• represents the s of atoms of each kind in a
  chem cmpnd by using atomic symbols and numerical
  subscripts

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A. Vocabulary
CHEMICAL FORMULA
IONIC
COVALENT
Molecular Formula
Formula Unit
CO2
NaCl
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• Molecular formula
• shows types and numbers of atoms combined in a
  single molecule

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-Formation of covalent bond

• Bond length
• aver dist between 2 bonded atoms
• Bond nrg
• nrg required to break a chem bond and form
  neutral atoms

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-The Octet Rule

• Octet rule
• 8 e-s in the highest nrg level

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-Lewis Structure

• (Gilbert Lewis)
• pg 169

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-Lewis Structure

• Unshared pair
• pair of e-s that is not involved in bonding
• single bond
• cov bond produced by sharing of 1 pair of e-s
  between 2 atoms

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• structural formula
• indicates kind, number, arrangement, and bonds
  of the atoms in a molecule.

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-Multiple Covalent Bonds

• Double bond
• cov bond between 2 atoms produce by sharing 2
  pairs of e-
• EX

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-Multiple Covalent Bonds

• Triple bond
• cov bond between 2 atoms produced by sharing 3
  pairs of e-
• Ex
• -Sample problem 6.3

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-Polyatomic Ions

• charged group of cov bonded atoms
• Ex

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6.3 Ionic Bonding and Ionic Compounds

• Ionic compound
• composed of and ions combined so that the
  and charges are equal

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6.3 Ionic Bonding and Ionic Compounds

• Formula unit
• simplest collection of atoms from which a cmpnds
  formula can be estab
• -Common ions
• Na, K,
• Mg2, Ca2, Ba2,
• O-2, S-2, F-,Cl-, Br-,I-

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-Formation of Ionic Bonds

• Lattice nrg
• nrg released when one mole of an ionic
  crystalline cmpnd is formed from gaseous ions

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-Ionic vs Covalent bonds

• -ionic bonds are stronger than cov bonds
• -cov bonds
• lower mp, bp, and hardness

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-Ionic vs Covalent bonds

• -ionic bonds
• hard and brittle
• carry a current when
• dissolved in water

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B. Types of Bonds
COVALENT
IONIC
e- are transferred from metal to nonmetal
e- are shared between two nonmetals
Bond Formation
Type of Structure
true molecules
crystal lattice
Physical State
liquid or gas
solid
Melting Point
low
high
Solubility in Water
yes
usually not
yes (solution or liquid)
Electrical Conductivity
no
Other Properties
odorous
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6.4 Metallic Bonding

• -metals have a low ionization nrg and low
  electroneg.
• -two metals form at best a weak covalent bond

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6.4 Metallic Bonding

• -metals tend to form what we call a sea of
  electrons

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6.4 Metallic Bonding

• Metallic bond
• chem bond resulting from the attraction between
  ions and surrounding mobile electrons
• -to compare strengths in metals vaporization
  heats are used

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B. Types of Bonds
METALLIC
e- are delocalized among metal atoms
Bond Formation
Type of Structure
electron sea
Physical State
solid
Melting Point
very high
Solubility in Water
no
yes (any form)
Electrical Conductivity
malleable, ductile, lustrous
Other Properties
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-Nature of Metals

• -the motion of the e- sea helps explain why
  metals have certain properties
• Malleability
• Ductility
• -luster

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B. Types of Bonds
RETURN
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B. Types of Bonds
RETURN
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B. Types of Bonds
Ionic Bonding - Crystal Lattice
RETURN
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B. Types of Bonds
Covalent Bonding - True Molecules
Diatomic Molecule
RETURN
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B. Types of Bonds
Metallic Bonding - Electron Sea
RETURN
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C. Bond Polarity

• Most bonds are a blend of ionic and covalent
  characteristics.
• Difference in electronegativity determines bond
  type.

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C. Bond Polarity

• Electronegativity
• Attraction an atom has for a shared pair of
  electrons.
• higher e-neg atom ? ?-
• lower e-neg atom? ?

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C. Bond Polarity

• Electronegativity Trend (p. 151)
• Increases up and to the right.

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C. Bond Polarity

• Nonpolar Covalent Bond
• e- are shared equally
• symmetrical e- density
• usually identical atoms

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C. Bond Polarity

• Polar Covalent Bond
• e- are shared unequally
• asymmetrical e- density
• results in partial charges (dipole)

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C. Bond Polarity

• Nonpolar
• Polar
• Ionic

View Bonding Animations.
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C. Bond Polarity

• Examples
• Cl2
• HCl
• NaCl

3.0-3.00.0 Nonpolar 3.0-2.10.9 Polar 3.0-0.92.1
Ionic
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6.5 The properties of molecular compounds
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-VSEPR Theory

• electrostatic repulsion between valence e- pairs
  surrounding an atom causes these pairs to be
  oriented as far apart as possible

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(table 6-5 pg 186)

1. Linear
2. Tetrahedral
3. Trigonal pyramidal
4. Bent

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-Hybridization(fig.6-23 p188)

• mixing of two or more atomic orbitals of similar
  nrgs on the same atom to give new orbital of
  equal nrgs

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-Hybridization

• ex CH4
• -hybridization of s and p yield 4 new identical
  orbits
• hybrid orbitals orb of nrg produced by the
  combination of 2 or more orb on the same atom

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-Intermolecular Forces

• force of attraction between molecules
• -generally weaker than the bonds that join atoms
  in molecules, ions in ionic cmpnds, or metal
  atoms in solid metals

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dipole-dipole forces and molecular polarity

• -strongest intermol forces act between polar
  molecules
• dipole but opp charges separated by a short
  distance.
• - arrow points toward the neg pole

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• DD force forces of attraction between polar
  molecules
• ex polar vs nonpolar

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hydrogen bonding

• an intermolecular attraction between a H atom
  and an unshared pair of e-s on a strongly
  electroneg. Atom

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hydrogen bonding

• -H bond represented by dotted lines connecting
  the H to the unshared e- pair of the electroneg
  atom

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london dispersion forces

• (Fritz London 1930)
• attraction resulting from the constant motion of
  e-s and the certain instantaneous dipoles and
  induced dipoles

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london dispersion forces

• -between all atoms and molecules
• -only intermolecular forces acting among
  noble-gas atoms and nonpolar molecules
• -LF increases with increasing mass of atoms and
  molecules