Bonding L11

Every wavelength of light is represented in the continuous spectrum

• Different energies=different colors - Every element produces different emissions/colors

• As wavelength/frequency changes, color changes • But light behaves like a wave and it behaves like a particle • As wavelength/frequency changes, the energy per photon changes

• Atomic orbitals on the same atom combine in order to form hybrids • Atomic orbitals on different atoms overlap in order to form covalent bonds • Each atom in the compound retains its associated orbitals and electrons • This theory correlates with observed bond angles in molecules

• Views molecules as a whole instead of a collection of individual atoms • MOs are similar to atomic orbitals • They both have specific energy levels • Atomic orbitals combine to form MOs • When two atomic orbitals combine, two MOs are formed • Orbitals are always conserved

• A MO that is lower in energy than any atomic orbitals from which it was derived • Electrons that occupy these orbitals cause stability

• A MO that is higher in energy that any atomic orbitals from which it was derived • Electrons that occupy these orbital cause instability

• A MO that is at the same energy level as the one atomic orbital it was derived from • Electrons that occupy these orbitals do not cause stability or instability • Orbitals that contain lone pairs

• A method of analysis which is based upon the absorbance of electromagnetic radiation by matter • Used to acquire data pertaining to the structure of a molecule or the concentration of a species

• Examines transitions in electronic energy levels • used to probe the electronic structure of certain compounds • used to determine concentrations of solutions that contain certain compounds

• Examines transitions in molecular vibrations - Is used to detect the presence of different types of bonds and to identify molecules

• An absorption spectrometer is used to measure the absorbance of a sample at wavelengths between 200 and 800 nm • The peaks represent wavelengths that correspond to the energy associated with possible electronic transitions within the molecule

• pi (bonding) to pi anti-bonding • pi non-bonding to pi anti-bonding • pi non-bondign to sigma anti-bonding

A=abc • A=absorbance • a=molar absorptivity (M-1cm-1) • b=path length of sample(cm) • c=concentration (M)

• all covalent bonds in molecules are vibrating • bond length is the average distance between nuclei • Covalent bonds have a vibrational frequency that is in the IR region of the electromagnetic spectrum • IR radiation of exactly the same frequency will be absorbed by the molecule • vibration frequencies depend on the mass of the atoms and the strength of the bonds • frequency is related to wavelength

• can be used to identify bond types, functional groups, and compounds • every compound has a characteristic IR spectrum that it can be identified through

opposite because it shows low transmittance=most absorbed