AP Chemistry Zumdahl Notes, 9 th ed. A Brief Collection of notes, Chapter 9 Feel free to open these files and annotate as you feel the need…this is for your success.

Covalent bonding: orbitals: hybrids and the localized electron model (building upon our knowledge of VSEPR, Lewis structures, etc.) sp 3 hybridization: figures on for illustration…main thing: note in figure 9.5…energy level of hybrids is in between s and p orbitals! Biggest take: atoms hybridize so as to achieve the lowest/minimal energy for the molecule Localized electron model…sounds to me like the hybrid orbitals that we would predict from VSEPR (different name, perhaps?) aps/Map%3A_Zumdahl's_%22Chemistry%22/08%3A_Bonding_General_Conce pts/8.09_The_Localized_Electron_Bonding_Model aps/Map%3A_Zumdahl's_%22Chemistry%22/08%3A_Bonding_General_Conce pts/8.09_The_Localized_Electron_Bonding_Model

more sp 2 hybridization: same thing, only one s and two p, leaving a p orbital as it was, which then is involved in a pi bond, perpendicular to the planar arrangement of the sigma bonded sp 2 orbitals Example: ethylene (properly, ethane) see page for pictures sp hybridization: same thing, only different, this time one s and one p, leaving two p orbitals for pi bonding…triple bond time, or two double bonds…see example, 422, for carbon dioxide, 423 for nitrogen dsp 3 hybridization: again, same thing, only different: one s, three p, one d, for five hybrid orbitals of equivalent energy, all for sigma bonds around the central atom…may have lone pairs occupying some of these orbitals d 2 sp 3 hybridization: wow…one s, three p, two d, for six equivalent orbitals; similarly, six locations for electron pairs, bonding or lone; illustrations on

Molecular Orbital Model Idea: overlap of atomic orbitals can form either bonding or anti-bonding molecular orbitals Intuitively, yes, the bonding molecular orbital is at a lower energy point (favoring bonded atoms), and the anti-bonding orbital is at a higher energy point (favoring separated atoms) Anti-bonding orbitals are labelled with an asterisk At its simplest: hydrogen molecule: both of these are referred to as sigma molecular orbitals: Bonding: MO 1 = 1s a + 1s b Anti-bonding: MO 2 = 1s a - 1s b

Molecular Orbital Model, continued Bond Order Bond order = (#bonding electrons -#anti-bonding electrons)/2 Bond order is an indication of bond strength, as it reflects the difference between bonding and antibonding electrons Large bond order number means greater bond strength Visit: _Orbital_Theory/How_to_Build_Molecular_Orbitals _Orbital_Theory/How_to_Build_Molecular_Orbitals

Bonding in Homonuclear Diatomic Molecules Bond order = 0 Consideration: bonding orbitals are establishing constructive interference, and antibonding orbitals are establishing destructive Think of the need for opposite spin designations for the electrons if sigma, same spin if pi…yes, this is something to remember If two overlapping orbitals are axial to the two atoms…sigma bond If two overlapping orbitals are parallel/above/below the two atoms…pi bond

Paramagnetism and diamagnetism Paramagnetic: a material attracted to a magnetic field Associated with unpaired electrons Diamagnetic: a material repelled from a magnetic field Associated with paired electrons If both present, paramagnetism will override, as its effect is stronger See figure 9.38, pg. 435…note filling of orbitals, magnetic effect, bond lengths Visit: al_Molecular_Orbital_Theory al_Molecular_Orbital_Theory

Bonding in Heteronuclear Diatomic Molecules Using molecular orbital diagram, fill in electrons, calculate bond order If they are contiguous on the PT, consider drawing as if homonuclear instead When the elements are further apart (very different), note illustration 9.42 on pg. 438 for thought: using only orbitals involved in bonding…interesting note is that fluorine’s 2p orbital is lower in energy than hydrogen’s 1s, showing tendency for fluorine to hold the electrons closer.

Combining the localized electron and MO models Reality check time: sigma bonds seem to be described reasonably well with the models, while pi bonds are more delocalized This allows us to feel more comfortable with what we are trying to describe Note figures , describing resonance structures We make this work out well Delocalization explains the behavior and bond lengths we observe in the molecules!

Photoelectron Spectroscopy (PES) Technique: high energy photons are directed at a sample, and a detector measures the energy of ejected electrons, which can be used to calculate the energy of the electrons in the sample E electron = hν – KE Realization: the peaks will correspond to the number of electrons present in the atom (height is directly proportional to #) See figures Visit: Spectroscopy/Photoelectron_Spectroscopy%3A_Theory Spectroscopy/Photoelectron_Spectroscopy%3A_Theory Demo site:

More sites for help UTF-8&hspart=mozilla&hsimp=yhs UTF-8&hspart=mozilla&hsimp=yhs Theory.pdf Theory.pdf