Columbia CHEM UN0001 - Chemical Bonds Formation of Compounds  from atoms

Unformatted text preview:

PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Chemical BondsFormation of Compounds from atomsPreparation for College ChemistryColumbia UniversityDepartment of ChemistryTrends in the Periodic Table Trends in the Periodic Table Lewis Structures VSEPR ModelAtomic Radii decrease going across a period from left to right, increases going down groupAtomic and Ionic RadiiIonization EnergyX(g)X+(g) + e-Minimum energy necessary to remove an electron from a neutral gaseous atom in its ground state (IE > 0, ground state stable system)∆E = IE1X+(g)X2+(g) + e-∆E = IE2First Ionization EnergiesElectron Affinity EAElectron attachment energy. Energy released when an atom in ground state gains a single electron.EAX(g) + e-X-(g)> 0< 0Gilbert Lewis. American ChemistFFFFF F FF 2s2p5P 2s2p3PLewis Structures of AtomsFOFF HThe Octect RuleIn H2O and HF, as in most molecules and polyatomic ions, nonmetal atoms except H are surrounded by 8 electrons (an octet). Each atom has a noble gas electronic configuration (ns2p6 )O FF-(2s2p6)Na +(2s2p6 ) NaIonic Bond. Electron Transfer+-Na+F-ClOIonic Bond. Electron TransfergClg]2+Cl-Cl-Mgg]2+O2-OAlAl]3+O2-AlOOAl]3+O2-O2-Ionicity vs. Covalency Covalent Bond. Sharing e-Energy1S11S1σ Bonding Molecular Orbitalσ∗ Anti Bonding Molecular OrbitalFFFF F FTwo p AO = TwoMOOnly bonding MO shownCollinear orbitals form  bondOFour p AO = TwoMO, and two Only bonding MO shownCoplanar orbitals form  bondOOOO OHElectronegativityClClHLinus PaulingFFNa+Cl-HClDipole03.3ClHLewis Structures of CompoundsCount valence electrons available.number of valence electrons contributed by nonmetal atom is equal to the last digit of its group number in the periodic table. (H = 1)Add electrons to take into account negative charge.Ex.OCl– ion: 6 (O) + 7 (Cl) + 1 (charge) = 14 valence e–CH3OH molecule: 4 (C) + 4(H) + 6 (O) = 14 valence e–Lewis Structures of CompoundsDraw skeleton structure using single bondsNote that carbon always forms four bonds.Central atom is written first in formula.Terminal atoms are most often H, O, or a halogen.Ex. O — Cl -HHH — C — O— HLewis Structures of CompoundsSubtract two electrons for each single bondO-Cl– ion: 14 – 2 = 12 valence e- leftCH3 OH molecule: 14 – 10 = 4 valence e- leftDistribute remaining electrons to give each atom a noble gas structure (if possible).O — Cl -HHH — C — O— HLewis Structures of CompoundsToo Few Electrons?Form multiple bondsEx. What is the structure of the NO3 – ion?Skeleton:N OOOvalence e– = 5(N) + 18 (3O) + 1(charge) = 24 e– Ovalence e– left = 24 - 6 (3 single bonds) = 18 e– Adding a double bond and rearranging:Resonance StructuresNitrate Ion (cont.)NO OONOOONOOOI II IIIMolecular GeometryVESPR principle:electron pairs around a central atom tend to be oriented so as to be as far apart as possible.BeF2 linear (2 pairs of e-) BF3 trigonal planar (3 pairs of e-) CF4 tetrahedral (4 pairs of e-) PF5 triangular bipyramid (5 pairs of e-) SF6 octahedral (6 pairs of e-)Molecular GeometryMoleculeLewis Str.Pairs of e-electronarrangem.MolecularShapeH2S4tetrahedralbentH S HCCl4CClClClCl4tetrahedraltetrahedralVSEPR


View Full Document

Columbia CHEM UN0001 - Chemical Bonds Formation of Compounds  from atoms

Download Chemical Bonds Formation of Compounds  from atoms
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Chemical Bonds Formation of Compounds  from atoms and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Chemical Bonds Formation of Compounds  from atoms 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?