Ionic Compounds

1
Ionic Compounds

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• Mr. Chan
• Northwestern University

2
Day 45

• (0-20) Error Analysis Ch.13 Quiz (half credit)
• (20-25) New Seats
• (25-35) Ch. 13 Syllabus check
• (35-43) Goals, Suggestions, Jobs
• (0-10) New Element Buddies
• (10-15) Warmup
• (15-35) Valence Electrons/Electron Dot Structures
• (35-43) HW Head Start

3
Determining Number of Valence Electrons and
Drawing Electron Dot Structures

• Valence Electrons
• Electrons in outermost energy level, (highest
  occupied energy level of element)
• Count number of electrons in highest energy level
  (n1,2,3,4)
• Use placement in group to determine valence
  electrons
• Important because largely determines chemical
  properties of an element
• Also, how an element will combine with another
• Electron Dot Structures
• Represent element, core electrons (symbol), and
  valence electrons (dots)
• Practice
• How many valence electrons?
• Potassium
• Carbon
• Magnesium
• Oxygen
• Now, draw electron dot structures

4
Day 46

• (0-5) Discuss HW
• (5-10) Warmup (Electron Dot Structures for
  Krypton, Rubidium)
• (10-30) Cations and Anions, Octet Rule
• (30-35) Summary, HW Head Start
• (35-43) 1st Quarter Review

5
Formation of Cations and Anions

• Remember those charges? How do we get those?
• Octet Rule (from observations/experiments)
• Atoms tend to achieve the electron configuration
  of a noble gas
• Duet rule hydrogen and helium
• Either gaining or losing electrons not protons
  or neutrons!

6
Cations and Anions

• Cations
• Lose valence electrons to achieve octet
• SHOW electron configuration of noble gas
• Ionization
• Recall ionization energy
• HONORS - Ions for transition metals
• Do not acquire noble gas configurations
• But, can achieve ones that are similar or
  reasonably full
• Formation of pseudo noble-gas configurations
• Anions
• Gain electrons to achieve octet
• Halide ions (halogens as ions)
• Electron affinity
• Examples
• Number of electrons gain or lose in forming an
  ion
• Na, F, Al, Ba
• Now, what is the formula of the ion?

7
Day 47

• (0-5) Discuss HW
• (5-10) Warmup
• (10-20) Formation of Ionic Bonds
• (20-30) Finish Stamp 4 Turn In
• (30-43) Properties of Ionic Compounds
• (0-5) Warmup 2 (Ionic Bond with Calcium and
  Chlorine)
• (5-10) HW Head Start
• (10-40) Go Fish! For Ionic Compounds
• (40-43) Prepare for Quiz

8
Characteristics of Ionic Bonds

• Ionic bonds
• Forces of attraction that bind oppositely charge
  ions
• Ionic compounds also called salts
• Show with electron dot structures (Na, Cl)
• Both ions achieve stable octets
• Note connections to chemical formulas
• Formula unit smallest sample of ionic compound
  that has the composition of the compound.
• Practice 7-8
• Examples
• Using electron dot formulas to predict formulas
  of ionic compounds formed from
• Potassium and iodine
• Calcium and sulfur
• Sodium and phosphorus
• Aluminum and oxygen

9
Properties of Ionic Compounds

• Most are solids at room temperatures
• Atoms or ions are arranged in repeating 3-D
  patterns
• Coordination number
• Number of ions of opposite charge that surround
  each ion in a crystal
• Very stable compounds
• high melting temperatures (SHOW)
• Conduct electric current (SHOW)
• As liquids, or in aqueous solutions
• Formula units, not molecules

10
Day 48

• (0-5) Discuss HW
• (5-15) Metallic Bonding,
• (15-35) Quiz

11
Metallic Bonding to Explain Physical Properties
of Metals

• Metals
• Closely packed cations and mobile valence
  electrons
• Metallic Bonds
• Attraction of free valence electrons for
  positively charged metal ions
• This is what holds metals together
• Properties explained
• Conductors of electrical current (SHOW)
• Ductility (SHOW)
• Malleability (SHOW)

12
Day 49

• (0-5) Return Quiz
• (5-15) Metal Alloys, Golden Penny
• (15-20) Warmup (H-Cl 2 nonmetals)
• (20-35) Covalent Molecules, Writing Lewis Dot
  Structures
• (35-43) HW Head Start
• (0-43) Ionic vs. Covalent Stations Activity

13
Crystal Structures and Alloys

• Crystal structures
• Body centered cubic
• Face centered cubic
• Hexagonal close-packed
• Coordination number of ion
• Number of ions of opposite charge that surround
  the ion in a crystal.
• Alloys
• Mixtures of 2 or more elements, 1 metal
• Sterling silver (92.5 Ag, 7.5 Cu
• Bronze (7 Cu 1 Sn)
• Steel (Iron, Carbon)
• Stainless Steel (80.6 Fe, 18Cr, 0.4C, 1Ni)
• Amalgams (Dental Filling Hg, Ag, Zn liquid
  that hardens quickly)

14
Covalent Bonding

• Single covalent bond
• Formed when a pair of electrons is shared between
  two atoms
• Take a look at some of the other diatomic
  molecules\
• NOTE metals vs. nonmetals, no charges, prefixes
  in names
• Structural formulas
• Show arrangement of atoms in molecules and
  polyatomic ions
• Molecular formulas vs. Formula units
• Lewis Dot Structures
• Sharing of electrons occurs if atoms can acquire
  the electron configurations of noble gases (OCTET
  RULE!)
• Shared and unshared pairs of electrons
• Unshared nonbonding or lone pairs

15
Day 50

• (0-5) discuss HW
• (5-10) Warmup Covalent bonds Br2, O2
• (10-20) Double and Triple Bonds
• (20-40) Complete Lab
• (40-43) HW Head Start

16
Double and Triple Bonds

• 2 or 3 shared pairs of electrons
• Still obeys octet rule
• Examples
• CO2
• N2, HCN

17
Day 51

• (0-10) Discuss HW clock buddies
• (10-25) Prelab isomers, molecular geometries,
  building models
• (25-43) Lab Molecular Modeling, finish other
  lab
• (0-43) Lab Molecular Modeling

18
Coordinate Covalent Bonding

• Recall CO example
• Coordinate covalent bond
• Formed when one atom contributes both bonding
  electrons in a covalent bond
• Dot Structures for Polyatomic Ions (HONORS)
• NH4 (loss of electron)
• SO3 2- (gain of electrons)

19
Resonance (HONORS)

• Draw electron dot structure for ozone, O3
• How do you know which structure is correct?
• Experiments show two bonds in ozone are same
  length
• Average of the two electron dot structure
  (hybrid, not resonating)
• More resonance structures more stability
• Resonance
• Two or more valid electron dot formulas can be
  written for a molecule

20
Exceptions to the Octet Rule

• Odd Numbers
• NO2
• Paramagnetic
• Relatively strong attraction to an external
  magnetic field
• Diamagnetic
• All of the electrons are paired
• Weakly repelled by an external magnetic field
• Incomplete Octet
• BF3
• Exceeding the Octet
• PCl5
• SF6

21
Relationship between Covalent bonding and orbital
diagrams

• H2O
• Show O and H orbital diagrams
• S from H and P from O overlap
• CO2
• S and P together leads into hybrid orbitals
  discussion (AP Only)
• Practice Drawing
• H2S
• PH3
• ClF
• HCN

22
Day 52

• (0-5) Discuss Lab, Review
• (5-25) Warmup
• (25-40) Shapes Part I
• (40-43) HW Head Start

23
Predicting the Shape of Molecules

• Using 3-D model as guide (molecular modeling
  lab), we could see how atoms arrange themselves
  outside of 2-dimensional drawings on paper
• CH4
• Tetrahedral, 109.5 bond angles
• VSEPR Theory
• Valence Shell Electron Pair Repulsion
• Molecular shape adjusts so the valence electron
  pairs are as far apart as possible.
• Tetrahedral, as opposed to a square for CH4
• Confirmed by experiment
• NH3
• Pyramidal, 107 degrees (lone pair repels bonding
  pairs)
• H2O
• Bent (planar), 105 degrees
• CO2
• Linear, 180 degrees no unshared pairs of
  electrons
• List of possible shapes
• Hybridization
• Formation of hybrid orbitals (sp3, sp2, sp)
• Examples
• CO2, SiCL4, SO3, SCL2, CO

24
Day 53

• (0-5) Warmup (Shape of CO2)
• (5-15) Review Shapes, Discuss Quiz
• (15-20) Discuss HW
• (20-35) Activity - Shapes Practice (whiteboards)
  And/Or
• Demos activate Polar vs. Nonpolar
• (35-43) Syllabus Check
• (0-10) Polar Bonds, Molecules
• Demo Sulfur on water
• (10-40) Rough Science Part 3
• (40-43) HW Head Start

25
Classifying as Polar, Nonpolar, or Ionic

• Not all covalent bonds are the same
• Nonpolar covalent bond
• Bonding electrons shared equally
• Polar covalent bond
• Bonding electrons shared unequally
• Two different elements may or may not be polar
• Recall electronegativity
• atoms strength of attracting electrons when
  shared
• Using electronegativity difference
• 0-0.4 nonpolar covalent
• 0.4-1.0 moderately polar covalent
• 1.0-2.0 very polar covalent
• 2.0 Ionic
• Note continuum ranges are approximate, not
  necessarily exact
• Examples
• What type of bond? (LAB)
• Mg-Cl, NH, K-I, F-F
• Practice 19-20
• Polar molecules

26
Day 54

• (0-5) Discuss HW
• (5-10) Warmup (CCl4)
• (10-20) Intermolecular Forces
• (20-35) Demos Making slime, oobleck and glurch?

27
Intermolecular Forces

• Weve seen what holds a molecule together, but
  what holds molecules together?
• Van der Waals forces
• Weakest attractions between molecules
• 1) Dispersion forces
• Weakest interactions
• Formed from temporary dipoles
• Exist in all molecules
• Br2, I2
• 2) Dipole-Dipole forces
• Occur when polar molecules attracted to one
  another
• Electrostatic attractions between partial
  positive and negative charges
• 3) Hydrogen bonding
• Hydrogen covalently bonded to very
  electronegative atom (F,O,N)
• Using IM Forces to explain molecular properties
• IM forces still weaker than ionic compounds
• Network solids all atoms covalently bonded to
  each other
• Diamonds (synthetic diamonds)

28
Day 55

• (0-10) Warmup/Review intermolecular forces
• Demo?
• (10-30) Powder Lab Ionic, Covalent Nonpolar
  and Polar Inquiry lab develop procedures
• (30-35) Ticket to Leave

29
Day 56

• (0-10) Discuss Review Sheet
• (10-20) Develop Jeopardy questions
• (20-30) Relay Summary
• (30-43) Organize Syllabus Check in
• (0-10) Synectics
• (10-43) Jeopardy
• 3x5 Notecard OK for test
• Review for Test

30
Day 57

• Chapters 1415 Test

31
Day 58

• Lab Practical Powder Lab

32
Molecular Orbital Theory

• Molecular orbitals hybridization
• Overlap of atomic orbitals to form hybrid
  orbitals
• Methane (CH4)
• 1 2s and 3 2p orbitals form four sp3 orbitals
• Each sp3 orbital overlap with 1s orbital of H
  atom
• Ethene (C2H4)
• Sp2 orbitals formed from 1 2s and 2 2p
• 3 sp2 orbitals single bonds between C-C and C-H
• Nonhybridized 2p orbitals (1 each C) overlap to
  form pi bond double bond
• Ethyne
• Try as example
• Sigma and Pi bonds
• Sigma symmetrical to axis between atoms
• Part of single bonds, first part of double bonds
• Pi bonds weaker than sigma bonds
• Part of double and triple bonds
• Bonding and Antibonding orbitals
• Bonding orbital molecular orbital with an
  energy lower than atomic orbitals formed from
• Antibonding orbital molecular orbital with
  energy higher than atomic orbitals formed from

33
Lab 25 Molecular Modeling

• Objectives
• Form 3-D models of covalent compounds
• Visualize the geometric shape of molecules
• Hypothesis
• Why are models useful in visualizing the
  structures of molecular compounds?

34
Covalent Compounds

• To insert your company logo on this slide
• From the Insert Menu
• Select Picture
• Locate your logo file
• Click OK
• To resize the logo
• Click anywhere inside the logo. The boxes that
  appear outside the logo are known as resize
  handles.
• Use these to resize the object.
• If you hold down the shift key before using the
  resize handles, you will maintain the proportions
  of the object you wish to resize.

• Mr. Chan
• Northwestern University

35
Lab Thin Layer Chromatography (TLC)

• Objectives
• Separate components of a mixture
• Observe pigments in vegetables
• Techniques
• Setting up chromatography chambers
• Making thin capillary tubes
• Spotting plates
• Developing plates
• No formal write-up
• Peer review of all labs and submit book at end of
  lab.