Bonds 10 1 13 Do not use prefix for ionic compounds Writing out Lewis Structue 1 Determine an arrangement of atoms i The atom with the fewest valence electrons is often the CENTRAL atom 2 Determine number of total valence electrons 3 Attach each bonded atom to the central atom with a pair of electrons 4 Place remaining electrons as LONE PAIRS to complete octets 5 If octets are not complete form a multiple bond by converting a lone pair to a bonding pair Sometimes single bonds DO NOT form a stable structure Carbon has only 6 electrons each oxygen has only 7 Four electrons shared is a double bond Two double bonds 8 electrons Bond itself is stable single bonds would not allow it to be stable Polyatomic ions Meomorized Held together by covalent bonds Follow the octet rule Be a net charge of an ion NO3 o Electron comes from somewhere Valence shell electron pair repulsion theory VSEPR Look at the shape of the molecule around the shape of the atoms Orbitals have electrons which repel one another Molecule will take on shape that will minimize repulsion Identify where negative charge is o Double single triple lone pair All are charge clouds Attached to CENTRAL ATOM Predict shape Draw lewis structure o Find central atom Count number of charge clouds Predict shape charge clouds want greatest distance between one another Two charge clouds Two charge clouds around C Repulsion is minimized when 180 degrees apart This shape is LINEAR Three charge clouds No loan pairs on central atom Planar triangular 120 degrees apart Boron Trifluoride Three charge clouds one loan pair So2 S has 3 charge clouds and 2 atoms bonded to O 120 degree bent angle Four charge clouds no lone pairs Four different groups reepeling Tetrahedral attangement Tetrahedral shape 109 5 degrees Four charge clouds one lone pair Methane 109 5 degrees Pyramidal shape Four charge clouds two lone pairs 109 degrees H20 Bent shape