SCH 4U: UNIT 8 LESSONS ATOMIC THEORY/BONDING & MOLECULAR ARCHITECTURE (Chap 7-pg 275, Chap 8 pg 325 & Chap 9-pg 367)

Size: px

Start display at page:

Download "SCH 4U: UNIT 8 LESSONS ATOMIC THEORY/BONDING & MOLECULAR ARCHITECTURE (Chap 7-pg 275, Chap 8 pg 325 & Chap 9-pg 367)"

Georgia Howard
5 years ago
Views:

1 SCH 4U: UNIT 8 LESSONS ATOMIC THEORY/BONDING & MOLECULAR ARCHITECTURE (Chap 7-pg 275, Chap 8 pg 325 & Chap 9-pg 367) 1. Rationale: This chapter looks at the theories that attempt to describe the inner structures of atoms and to explain how atoms combine to form compounds. 2. REVIEW a) Atomic spectra and the Bohr model (from SCH3U) (7.2-pg 282) - why the Bohr model was abandoned Heisenberg 1 b) Energy Level diagrams & electron configurations? (7.5/6-pg 295) c) Shapes of atomic orbitals demo with balloons (7.8 pg 303) 3. Electron Waves in atoms Quantum Numbers (7.3 pg ) a) debroglie & Schrodinger b) The 4 Quantum numbers 1) The Principal Quantum # n Ranges from n=1 n=7, designates the shell or energy level that the electron is in, corresponds to the periods on PT 2) The Secondary quantum # l Value l=0 l=(n-1) Divides the energy levels into sub-levels ie orbitals l=0 s orbital; l=1 p orbital etc 3) The Magnetic quantum # m l Value +l 0 l Divides the sub-levels into individual orbitals ie p x orbital 4) The spin quantum # m s Value +1/2 or 1/2 Accounts for the fact all electrons are spinning on their axes c) Do several examples of electron configurations with quantum # s designating the location of the electrons (see table 7.1 pg 292) * Pauli exclusion Principle 4. Variation of Atomic Properties with Electron Structure (7.9 pg ) a) Size of Atoms & Ions (pg ) b) Ionization Energies (pg ) c) Electron Affinity (pg ) ASSIGN

2 Chem Luminescence DEMO (in the photography darkroom) Requires: a) 3 tall cylinders ( water, water + rescorcinol, water + fluoroscein ) Mix: 4 g hemoglobin 4 g sodium perborate 30 g sodium phosphate tribasic 30 g icing sugar 0.2 g luminal b) lightsticks ( 1 bright, 1 red, 1 blue + light sensitive paper c) blacklight + rock collection + 2 soaps ( 1 normal, Cheer) + tonic water + wintergreen certs + chem. T-shirt ** CHEMICAL BONDING: General Concepts (Chap 8 pg ) 5. The Chemical Bond. Why does it form?? Atoms form aggregates to lower their energy and increase their general stability-a true chemical bond involves a drop of ~ 40 kj/mol of energy Ex: 2 H H 2 H=-436kJ/mol (H 2 much more stable than 2 H) 2 He He 2 H = +ve (doesn t form!!) Hydrogen bonds = kj (enough to form but not considered true bonds) 6. Electron Transfer Formation of IONIC COMPOUNDS (8.1 pg 325) - Atoms gain or lose electrons to become charges particles IONS. Resulting ions are held together by electrostatic attraction F es = q 1 *q 2 /r 2 Show some examples - conditions that favour formation of ion compounds (8.1 pg 326) - Importance of the Lattice Energy (8.1 pg 326) 7. Electron Sharing Formation of COVALENT BONDS (8.3 pg 333) Atoms SHARE electrons to complete energy levels creating a common attraction to the shared pair covalent bond. Do several examples from 3U ( single, double & triple ) * +++ co-ordinate bond Discuss bond length & bond strength illustrate with Morse Curve diagrams see overhead H + 2 & H 2 molecules Discuss Bond POLARITY (8.5 pg 340) Discuss Resonance in molecular structures (8.9 pg 354)

3 8. MOLECULAR ORBITAL THEORY LCAO (9.7 pg 404) a) * When a bond forms 2 atomic orbitals overlap creating 2 new regions of space (orbitals) for the electrons called molecular orbitals i) sigma molecular orbital: the electron density ( 3-dim ellipse) is between the nuclei ( this bonding molecular orbital tends to stabilize a molecule ( energy is lower) ii) sigma* anti-bonding molecular orbital: the electron density does not lie between the nuclei ( this anti-bonding molecular orbital tends to destabilize a molecule (energy is higher) -draw diagrams of the orbitals ( use balloons as well) - use 9.7 in book excellent diagrams - polar bond diagrams b) Multiple Bond formation: pi(π) bonds illustrate with balloons -incorporate into MO diagram with p orbitals - sketch on board using O 2 then N 2 etc c) Molecular Orbital diagrams (pg 405 & 407) illustrate using H 2 then He 2, He 2 +, O2, N 2, NO etc d) Paramagnetism: discuss, illustrate with O 2 vs diamagnetism ferromagnetism e) Bond order: (pg 406 ) discuss, illustrate with O 2, N 2 & NO. 9. BONDING Across a PERIOD Family IA o All end s 1, low ionization energy o Form primarily ionic bonds especially as you move down the family Family IIA o All end s 2, medium ionization energy o Form primarily ionic bonds especially as you move down the family but o Forms BeH 2 2 equal strength/length bonds HOW? form sp hybrids (draw shape) & illustrate orientation. Now apply to BeH 2 and show the shape to be linear (ex-pg 368) (see pg ) * note: BeH 2 still has 2 empty p orbitals so can easily form co-ordinate bonds and potentially act as a Lewis acid

4 Family IIIA o All end s 2 p 1, ionization energy getting too high except near bottom of family o Form primarily covalent bonds except near bottom of family -3 bond molecules o Forms BH 3 & AlH 3 & AlCl 3 3 equal strength/length bonds HOW? form sp 2 hybrids (draw shape) & illustrate orientation. Now apply to BH 3 and show the shape to be trigonal planar (ex-pg 368) (see pg 390) * note: BH 3 & AlCl 3 still have 1 empty p orbital so can easily form co-ordinate bonds and potentially act as a Lewis acid o *the tendency to form dimers ie B 2 H 6 & Al 2 Cl 6 Family IVA o All end s 2 p 2, ionization energy getting too high except very bottom of family o Form primarily covalent bonds including bottom of family -4 bond molecules o Forms CH 4 & SiCl 4 4 equal strength/length bonds HOW? form sp 3 hybrids (draw shape) & illustrate orientation. Now apply to CH 4 and show the shape to be tetrahedral (ex-pg 368) (see pg ) * note: CH 4 do not have any empty p orbitals so cannot easily form other bonds o *illustrate the versatility of carbon forming sp, sp 2 & sp 3 hybrids forming carbon compounds with all single bonds(all sigma) ie CH 4 or C 2 H 6. (sp 3 ) 2 singles & 1 double bond(3 sigmas + 1 pi) ie CH 2 O or C 2 H 4. (sp 2 ) (see pg ) 2 doubles or 1 single & 1 triple (2 sigmas & 2 pi ) ie CO 2 or HCN or C 2 H 2 (sp) (see pg )

5 Family VA o All end s 2 p 3, electron affinity now increasing at top of family negative ions o Form primarily covalent bonds -3 & 5 bond molecules o Forms PCl 3 & PCl 5 3 & 5 equal strength/length bonds HOW? form sp 3 hybrids (draw shape) & illustrate orientation. Now apply to PCl 3 and show the shape to be trigonal pyramid because of the lone pair or nonbonding pair of valence electrons(ex-pg 374) (see pg 382) * note: PCl 3 has 1 lone pair in a sp 3 hybrid orbital so can easily donate this pair to another with an empty orbital acts a good lewis base o *illustrate the ability of phosphorus ( but not nitrogen) to use its d orbitals Family VIA to form sp 3 d hybrids creating PCl 5 a molecule with 10 electrons around the central atom forming a trigonal bipyramid shape (ex-pg 369) ( pg 380 & 393) illustrate what happens when lone pairs are introduced to this shape. (ex-pg 375)) o All end s 2 p 4, electron affinity now high at top of family form negative ions o Form primarily covalent bonds -2 up to 6 bond molecules o Forms OH 2 & SCl 6 2 & 6 equal strength/length bonds HOW? form sp 3 hybrids (draw shape) & illustrate orientation. Now apply to OH 2 and show the shape to be bent because of the 2 lone pairs or non-bonding pair of valence electrons (ex-pg 374) (see pg 396) * note: SCl 2 has 2 lone pairs in sp 3 hybrid orbitals so can easily donate this pair to another with an empty orbital acts a good lewis base o *illustrate the ability of sulfur ( but not oxygen) to use its d orbitals to form sp 3 d 2 hybrids creating SCl 6 a molecule with 12 electrons around the central atom forming an octahedral shape (ex-pg ) ( pg 380) illustrate what happens when lone pairs are introduced to this shape. (ex-pg 376)

6 Family VIIA o All end s 2 p 5, electron affinity now very high for top of family form negative ions o Form a lot of covalent bonds -1 up to 7 bond molecules o Forms HF & IF 7 1 & 7 equal strength/length bonds HOW? form sp 3 hybrids (draw shape) & illustrate orientation. Now apply to HF and show the shape to be linear because of the 3 lone pairs or non-bonding pair of valence electrons o *illustrate the ability of iodine ( but not fluorine) to use its d orbitals to form sp 3 d 3 hybrids creating IF 7 a molecule with 14 electrons around the central atom forming an pentagonal bipyramid shape illustrate what happens when lone pairs are introduced to this shape. Family VIIIA o All end s 2 p 6, very stable electron config but can form covalent bonds especially near bottom of family o Illustrate with XeF 4 9. BONDING IN SOLIDS (9.9 pg 411) Handout: Characteristics of Crystalline solids Discuss 4 types of solids **ASSIGN * Take-Home quiz: Bonding exercise

Chemistry 121: Topic 4 - Chemical Bonding Topic 4: Chemical Bonding

Chemistry 121: Topic 4 - Chemical Bonding Topic 4: Chemical Bonding Topic 4: Chemical Bonding 4.0 Ionic and covalent bonds; Properties of covalent and ionic compounds 4.1 Lewis structures, the octet rule. 4.2 Molecular geometry: the VSEPR approach. Molecular polarity.