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Lewis Theory

Lewis Theory. February 15 th 2011 Mr. Dvorsky SCH4U1. Lewis Theory. Useful system for keeping track of valence electrons of elements is the Lewis electron dot symbol.

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Lewis Theory

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  1. Lewis Theory February 15th 2011 Mr. Dvorsky SCH4U1

  2. Lewis Theory • Useful system for keeping track of valence electrons of elements is the Lewis electron dot symbol. • In this notation the nucleus and core electrons are represented by the atomic symbol. The valence electrons, represented by dots, are then placed around the symbol one at a time until all four sides are occupied.

  3. Lewis Theory • The nobel gas configuration with 8 valence electrons is the stable, low-energy state • The behaviour of elements can often be considered the result of gaining, losing, or sharing valence electrons to achieve the same configuration as the nearest nobel gas. • Since all the nobel gases (except He) have 8 valence electrons, we call this the octet rule.

  4. Lewis Theory • The valence electrons of an atom are labelled based on whether they are single or paired in orbitals. Single or unpaired electrons are called bonding electrons. The paired electrons are called lone pairs. The number of chemical bonds an atom can form is a function of its number of unpaired electrons. The term for the number of bonds an atom can form is bonding capacity

  5. Lewis Theory • Fill in chart at top of handout • See steps for the writing of Lewis structures

  6. Valence Bond Theory • Schrodinger described wave functions for an electron that were used to construct a particular volume of space (orbital) in which the probability of finding an electron is high. • Visualized as electron clouds with characteristic shapes and orientations • An atom has only one nucleus to consider but a molecule has two or more nuclei to take into consideration

  7. Valence Bond Theory • In valence bond theory, a covalent bond is formed when two orbitals overlap to produce a new combined orbital of two electrons with opposite spin. • This arrangement results in a decrease in the energy of the atoms forming the bond.

  8. Valence Bond Theory • e.g. The 1s orbitals of two hydrogen atoms overlap to form the single covalent bond of the hydrogen molecule.

  9. Valence Bond Theory • HF

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