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LectureNotes2461 - Chemistry 2461 Fall 2008 Dr. G. Vicente...

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Unformatted text preview: Chemistry 2461 Fall 2008 Dr. G. Vicente 1 LECTURE NOTES FOR CHEMISTRY 2461 Fall 2008 Chemistry 2461 Fall 2008 Dr. G. Vicente 2 CHAPTER 1: ELECTRONIC STRUCTURES AND BONDING Organic Chemistry is the study of carbon compounds. Carbon is unique in its versatility (later).. Atomic structure (1.1) Atomic number (Z) : number of protons in the nucleus of an atom. Mass number (A) : total number of protons and neutrons in the nucleus of an atom. Isotopes : have the same Z but different mass numbers. Atomic orbitals : region of space around the nucleus where the probability of finding an electron is very high. AOs have characteristic shape, size and energy. Orbitals that have the same energy are degenerate orbitals . Electron configuration of atoms (1.2) Rule 1 (aufbau principle) : orbitals are occupied in order of increasing energy (1s<2s<2p<3s<3p<4s<3d.) Rule 2 (Paulis exclusion principle): only 2 electrons can occupy an orbital and they must have opposite spin ( ). Rule 3 (Hunds rule): when there are degenerate orbitals, one electron is added to each with their spins parallel until all are half full. Then a second electron with opposite spin is added to each degenerate orbital. Octect rule : tendency to have 8 electrons in the outermost (valence) shell, which is a very stable, noble-gas, configuration. Hydrogen only requires a duet (2 electrons) to achieve He electronic Chemistry 2461 Fall 2008 Dr. G. Vicente 3 configuration. Exceptions to the octect rule: for example BF 3 and PCl 5 Chemical bonds (1.3) Ionic bonds : formed by the transfer of one or more electrons from one atom to another to create ions, which electrically attract each other. Li-e Li with filled shell F +e F with filled shell (octet) ionic compound Li F Ionization energy : energy required to remove an electron from an atom. Electron affinity : energy released when an atom acquires an electron. Covalent bonds : formed when atoms share electrons. F F F F covalent compound Non-polar covalent bonds : the electrons are equally shared. The electronegativity of the two atoms is the same or very similar (example: Cl 2 ). Polar covalent bonds : the electrons are not equally shared. The electronegativity of one atom is greater than the other (example: HCl). Electronegativity : ability of an atom to attract electrons. Chemistry 2461 Fall 2008 Dr. G. Vicente 4 Dipole moment ( )=magnitude of charge ( e ) x distance between charges ( d ) Partial positive and negative charges are represented by + and - Representation of structure (1.4) Lewis dot structures : represent the valence electrons of an atom by dots. Kekul or line-bond structures : each dash represents a pair of electrons....
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LectureNotes2461 - Chemistry 2461 Fall 2008 Dr. G. Vicente...

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