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What are we going to learn today? −Electron Configuration and Bonding
- Employ the concept of resonance
- Use formal charge to help predict best
SPARKS CH301 ELECTRONS and COMPOUNDS UNIT 2 Day 8 What are we - - PowerPoint PPT Presentation
SPARKS CH301 ELECTRONS and COMPOUNDS UNIT 2 Day 8 What are we - - PowerPoint PPT Presentation
SPARKS CH301 ELECTRONS and COMPOUNDS UNIT 2 Day 8 What are we going to learn today? Electron Configuration and Bonding Employ the concept of resonance Use formal charge to help predict best possible Lewis structure INDIVIDUAL
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Naming Compounds Choose the formula that corresponds to: strontium and phosphorus.
a) SrP b) SrP2 c) Sr2P d) Sr3P2 e) Sr2P3
INDIVIDUAL QUIZ: NO TALKING!
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Naming Compounds Choose the formula that corresponds to: potassium dichromate. a) KCrO4 b) KCr2O7 c) K2CrO4 d) K2Cr2O7 e) K3Cr2O
INDIVIDUAL QUIZ: NO TALKING!
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Naming Compounds Choose the formula that corresponds to: sulfur trioxide. a) SO b) SO3
2-
c) SO3 d) S2O3 e) SO4
2-
INDIVIDUAL QUIZ: NO TALKING!
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Naming Compounds Choose the formula that corresponds to: sulfite. a) SO b) SO3
2-
c) SO3 d) S2O3 e) SO4
2-
INDIVIDUAL QUIZ: NO TALKING!
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Naming Compounds Choose the name that corresponds to: NH4OH. a) nitrogen tetrahydrogen oxygen hyrdride b) nitrogen pentahydrogen oxide c) ammonium hydroxide d) ammonia oxyhydrogen e) hydronitrideoxide
INDIVIDUAL QUIZ: NO TALKING!
SLIDE 8
Course packet p. 44
Finish that? Here are some more structures to try: PCl3 CH3CH2OCHCH2 NH2CH2CHCH2 XeF4
SLIDE 9
Used when more than one Lewis structure can be
- drawn. Determines which is most plausible.
Formal Charge check
# valence electrons # nonbonding electrons + # shared electrons 2 F.C. =
- Sum of the FC’s for all atoms = overall charge
(zero for neutral molecule)
COCl2: Which Structure is Best?
SLIDE 10
- Essentially, we are comparing
– the number of valence electrons in the neutral, free atom WITH – The number of valence electrons “belonging” to the atom in a molecule.
- Assumptions:
– Lone pairs belong entirely to the atom. – Bonding pairs are divided equally
SLIDE 11
Put these on the board...Working for candy and fame
NO3
SLIDE 12
Resonance structures for the formate ion are shown below. An average C-O single bond is 0.143 nm in length An average C=O double bond is 0.123 nm in length. Which choice describes the actual bond lengths for the carbon-oxygen bonds in a formate ion?
- A. Both carbon-oxygen bonds are 0.133 nm.
- B. Both carbon-oxygen bonds are 0.143 nm.
- C. One carbon-oxygen bond is 0.143 nm and the other is 0.123 nm.
- D. Both carbon-oxygen bonds switch between 0.123 nm and 0.143 nm.
POLL: CLICKER QUESTION
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Think about it …. Ionic or covalent?
NaOH
SLIDE 14
Compounds of Polyatomic Ions: Within the ions: bonding between atoms is covalent but overall bonding between ions in the crystal is ionic.
SLIDE 15
Just when you were sure you had it nailed…
RnCl2 BeCl2
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Exceptions to Octet Rule
- Be: 4 e- needed, BeCl2
- B: 6 e- needed
- Odd number of electrons in molecule
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- 1. How many resonance structures are there for
- zone, O3? (Note, this is not a cyclic molecule,
which will be discussed later.)
- A. 0 B. 4
- C. 2
- D. 3
- 2. Which bonds would be stronger: those in ozone
- r those in oxygen (O2)?
- A. the bonds in ozone
- B. the bonds in oxygen
- C. one bond in ozone will be equal in strength to the
- xygen bond; the other ozone bond will be weaker
than the oxygen bond.
POLL: CLICKER QUESTION
SLIDE 18
Consider NOCl, in which the least electronegative element is the central atom. The dot structure has a
- A. N-Cl single bond
- B. N-Cl double bond
- C. N-Cl triple bond
SLIDE 19
What have we learned?
ATOMS BEHAVE IN CERTAIN PREDICTABLE WAYS WHICH CAN BE CORRELATED TO THE ELECTRON CONFIGURATIONS SATISFYING THE OCTET RULE IS A SOLID PREDICTOR OF BONDING IN IONIC AND COVALENT COMPOUNDS RESONANCE IS THE AVERAGE OF THE EXTREMES – ELECTRONS ARE NOT TRAPPED IN THE LITTLE DASHES FORMAL CHARGE HELPS PREDICT BEST LEWIS STRUCTURE FOR A GIVEN MOLECULAR FORMULA
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Learning Outcomes
Draw the Lewis structures for molecular compounds and ions. Use Lewis structures to predict and explain the relative bond Strength and lengths in compounds. Recognize and apply exceptions to the octet rules. Draw resonance structures for a molecule or polyatomic ion. Apply formal charges to structures and use them to predict the most likely structure.
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