Chem 112 Exam AID Course Pack

Electrons are shared between two atoms the atoms are

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Unformatted text preview: multiple orbitals that have the same energies Nodes: used to describe the shape of the orbitals, a node is implemented when there is a change from a positive lobe to a negative lobe In general orbitals have n- 1 nodes Pauli- Exclusion Principle: No two electrons can have the same set of quantum numbers Filling orbitals: Ethan Newton & Barry Zhang for SOS Winter 2012 7 Hunds Rule: Electrons are placed in unpaired p, d, f suborbitals until each orbital has one electron Aufbau’s Principle: Electrons are placed in the lowest energy orbitals first until all suborbitals are filled Noble Gas Abbreviation: Can use the noble gas in the row above to represent the core electrons followed by the valence electrons Lewis Diagrams A chemical bond is an interaction that holds two (or more) atoms together in a molecule. - involve a pair of valence electrons, which may originally come both from the same atom or one from each - the valence electrons are those in the s and p orbitals (so the maximum number is 8) - elements in the first column of the periodic table (H, Li, etc) have one valence electron; in the second column (Be, Mg, etc) they have two; in the third (B, Al, etc) they have four; and so on (note that this considers the main group elements only – those with no unfilled sets of d or f orbitals) - elements with 1 or 7 valence electrons are particularly reactive (hence the reaction of alkali metals with water, and why halogens exist in pairs as F2, Cl2, etc) In covalent bonds, the electrons are shared between two atoms - the atoms are held together by the attraction of both atoms to the shared electrons - the electrons will on average be closer to the atom which is more electronegative - (if the other atom is too electronegative, though, it will take the electrons entirely, producing an ionic bond instead) - for example, carbon can make four covalent bonds Ethan Newton & Barry Zhang for SOS Winter 2012 8 In ionic bonds, the electrons are transferred - results in two ions, which are then held together by electrostatic interactions - the ions may be carried apart (especially in solution) - in the solid phase, will take a crystalline form with alternating positive and negative ions in a large network - occur especially between alkali metals and halogens, ex NaCl In Lewis structures, atoms are depicted as their atomic symbol, with electrons around them representing the valence electrons - other electrons are ignored, as they are unreactive - remember that these electrons will normally act in pairs - elements in the same column o...
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This note was uploaded on 10/02/2012 for the course CHEM 112 taught by Professor Carran during the Winter '08 term at Queens University.

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