Types of Bonds

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Types of Bonds

• Covalent (2 types)
• Ionic
• Metallic
• Covalent network
• 20 min movie for each type

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Chemical Bonding

• What is a chemical bond?
• What is a covalent bond?
• What is an ionic bond?
• How do we measure the degree of ionic or covalent
  character of a bond?
• Electronegative difference table p. 151

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Electronegativity Difference and Bond Type

• Bond type
  Electroneg.diff ionic character
• Nonpolar covalent
• (equal share)
• Polar covalent
• (unequal share)
• Ionic
• (transfer)
• Workbook C1-10

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What about ClAg?
AgCl Cl2
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Type 1 Covalent Bonds (2 kinds nonpolar and polar)
Nonpolar Bonds
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Type 1 Covalent Bonds (2 kinds nonpolar and
polar)
Covalent Skeleton HO, top half only
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Type 2 Ionic Bonds
Bottom half skeleton
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Ionic Bonding Video (20min) and Bonding in
Molecules (covalent) 20min) with HOs
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More on Covalent Bonds ?Why would 2 atoms
surrounded by electrons ever form a bond?
?Formation of covalent bond happens when
potential energy is ____
Covalent skeleton
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• What is the sign of bond energy?
• As bond length decreases, bond energy?

• Unit of bond length
• Units bond energy

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What is bond length? What is bond energy?
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Lets form a covalent bond, covalent bonds use s
and p electrons Stable octet (2s 6p electrons
?)
You try H-F and O2
Exceptions to octet rule H He (2 es) Be (4
es) B (6 es)
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There is an easier way to show a bond, use
electron dot structures
Review Basic Dot Notation
Review Whats the electron dot notation for Po,
Cu, Fr, I?
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Electron dot structures for molecules

• CH4
• CBr2H2
• H3O
• Practice Time try some from
• Grid sheet columns 1-3
• Finish up grid for homework
• and wkbk C11-C15

• Count the total valence es
• Pick central atom (C or most electropositive
  element)
• Each bond 2 es
• Attach other atoms (start with single bonds)
• Evaluate (count up es used and octet rule
• What is the octet rule

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Multiple Bonds

• Try single bonds 1st. A double bond corrects for
  a deficiency of 2 e-s.
• Occasionally a triple bond is needed. It
  corrects for a deficiency of 4 e-s

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Exceptions to the Octet Rule

• Mlcls with odd number of valence e-
• Be and B complete with less than 8 Be with 4
  e- and B with 6 e-
• Expanded octets for some elements of periods 3 or
  higher. May have 10 or 12 val e-. Why not periods
  1 or 2?

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Bond Energy and energy of reaction

• Calculate the energy for the formation of HCl
  from diatomic hydrogen and diatomic chlorine,
  using bond energies.

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Resonance

• 1. Resonance does not imply different kinds of
  mlcls but the true structure is between each
  resonance form.
• 2. Try resonance when it is possible to write 2
  or more plausible Lewis structures.
• 3. In resonance forms, e-s not atoms are
  shifted.
• Clue look for mlcls with ________ to see if
  resonance is likely

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Molecular Geometry

• The properties of molecular compds depend on
  bonding and on molecular geometry

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VSEPR model

• Valence Shell Electron Pair Repulsion (Sidgwick
  and Powell 1940 and expanded by R.J. Gillespie in
  Canada
• The electron prs surrounding an atom will repel
  one another and are oriented as far apart as
  possible.

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VSEPR theory (contd)

• Always look at Central Atom (CA) and see
  electron pairs on it.
• Examine bond angles, position of other atoms
  relative to CA
• Identify shape of mlcl as linear, bent, or
  tetrahedral etc.

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Foam models
Grid sheet Columns 4 5 Workbook C16
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Lone pair electrons will decrease the central
angle by 2 degrees per lone pair electrons
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Hybridization

• VESPR Theory useful to explain molecular shape.
• DOES NOT relate geometry to bonding orbitals (s
  and p)

• Hybridization explains how orbitals rearrange
  when forming a covalent bond.

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Hybridization (contd)

• Summary
• bonds atomic hybrid
  geometry ex .
  orbitals orbitals
• s, p sp linear BeF2
• s, p, p sp2
  planar BF3
• s,p,p,p sp3
  tetrahedron CBr4

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Dry Lab Activity

• Molecular Model Handout

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Polarity of molecules

• What is a polar molecule?
• What is a nonpolar molecule?
• Molecular polarity depends on _________ of each
  bond and __________ of each bond.

Columns 67 Workbook C18-20
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Individual bonds can be polar but the overall
molecule is nonpolar. How can this be?
For this class any molecule with a charge is
polar (H3O)
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Polarity

• H2
• OCl2
• CHF2
• N2

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More on Type 2 Ionic Bonds
NaCl CN 16 CsCl CN 18
Ionic compounds exist as 3-d networks composed on
many ions yielding crystal solids.
Ionic skeleton
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Ionic Bonding

• What is ionic bonding?
• Transfer of an electron between 2 atoms (a metal
  and a nonmetal)
• Formula unit
• We can use an electron dot structure to show an
  ionic bond

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Ionic Bonding (contd)

• Lattice Energy-
• What sign are the values and why?
• Isoelectronic-

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Ionic Compounds

• Orbital Notation

• Lewis Dot Structure

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Type 3, Metallic Bonding

• What is it?

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Metallic Bonds

• In solid and liquid metals, metal atoms give up
  e- s which are free to move through the material
  due to space in valence shell not held in place
  between 2 atoms as in ionic bond.

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Metallic Bonding (contd)

• Answer the following
• Why are solid metals better conductors than
  molten ionic cmpds?
• Why are metals excellent conductors (thermal
  electrical)?
• Metallic Bonds (22min) and Bonding between
  Molecules (20 min) w HOs

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Metals

• Why are the electrons so mobile?
• Why are they ductile and malleable?
• Why do metals have a luster?

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Metallic Bonds

• P.182 Compare the heats of vaporization
• Explain the trend for heats of vaporization down
  group 1 and across period 3 (does it increase or
  decrease and why?

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Comparing the 3 kinds of bonds (covalent, ionic,
metallic)

• Usually
• Metal atom to nonmetal atom is___
• Nonmetal to nonmetal atom is ___
• Metal to metal atom is ___
• Why do chemical bonds occur?
• Text p195 1-7 p196 33-36

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Type 4, Network Covalent Solids

• So far we discussed molecular compounds that
  consist of individual molecules network covalent
  solids have a continuous, 3-d network of
  covalently bonded atoms GIANT molecules without
  distinct units simplest ratio of atoms keeps
  repeating throughout.
• A specialized type covalent bonds

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Network Covalent Solids

• Diamond (Cx) or (SiO2)x
• Very strong bonds

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Intermolecular Forces

• What are intermolecular forces?
• How does their strengths compare to ionic,
  covalent or metallic bonds?
• How does the strength of the force affect boiling
  points?

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Intermolecular Forces (contd)

• A) dipole-dipole forces
• Example
• What is a dipole?
• Example

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Intermolecular Forces Contd

• B) Hydrogen bonding
• Hydrogens size is______
• Large
• Causes an
• Examples - HF, H2O, NH3

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Intermolecular Forces (contd)

• C) London dispersion forces
• Intermolecular attractions
• Even found in
• Act between
• Only intermolecular forces among _______ and
  ____________
• P. 190 compare forces and bp

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Lets fill in a table

• Volatile m.p.
  Elect.Cond. H2O solub Forces within Forces
  between
• Ionic (NaCl) 
• Molecular 
• Nonpolar
• (O2) 
• Polar
• (NH3)
• (H2O) 
• Network covalent
• (diamond Cx)
• (quartz SiO2(x)) 
• Metallic
• (Fe, Cu)
•