KSU CHEM 1211 - Principles of Chemistry Review for Exam 2

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Principles of Chemistry 1 Dr K By Gabriella Erickson Review For Exam 2 Periodic Table Trends Across Period L to R Zeff Effective Nuclear Charge Atomic Radius Electron Affinity Ionization Energy Ionization Energy Electronegativity General Terms Bonding Capacity The amount of bonds that can still be formed with an atom after considering the number of valence electrons it has Electron Affinity energy change associated with the addition of an electron Halogens Group 7A have the most favorable Reverse of Ionization Energy Atomic Radius Half the distance from the nuclei of 2 of identical same atoms Cations in Radius and Anions in Radius from their parent atom o K K and Cl Cl Isoelectronic Series atoms and ions that contain the same number of electrons o Example Ar Cl S2 all have same e numbers Lattice Energy The energy created from the formation of one mole of ionic compound Formula 2 Effective Nuclear Charge Zeff Net Positive Charge experienced by electrons in a subshell Zeff Z S o Z is the number of protons in the nucleus o S is the number of electrons blocking nucleus In a family column The Zeff is the same Formal Charge Charge each atom has by assuming electrons are divided equally between bonded atoms In an ionic bond you don t need to calculate because the formal charges are already there as they are ions Covalent has partial charges because the electrons are shared not transferred This formula calculates what their formal charge would be if they did trade FCatom atom s valence e unshared e shared e Bond Energies Ball and Stick Diagrams Energy required to break one or more bonds in the gas phase As Bond Order increases so does the Bond Energy 3 Types of Bonds Ionic o Occurs between a cation and an anion where formal charges create an overall neutral charge Usually metals and non metals but not always o Cation o Anion Covalent An ion which has a positive formal charge An ion which has a negative formal charge o Bond occurs between non metals where electrons are shared o Types Bond has a dipole pulls electron closer to itself causing an Polar Covalent asymmetrical shape Non polar Covalent Bond s do not pull more to one side or another and has symmetrical shape Metallic o The Bonds formed within a metal and between metals 4 Naming Compounds Ionic o Keep the first element name the same o The last element ends in ide o If a transition metal add the charge I II III etc Covalent o Add prefixes to all atoms in the compound 1 Mono 2 Di 3 Tri 4 Tetra 5 Penta 6 Hexa 7 Hepta 8 Octa 9 Nona 10 Deca 5 o The last element ends in ide o If the first element beings with prefix mono it isn t necessarily needed Octet Rule Exceptions Expanded Valence Shells Period 3 or higher atoms can have expanded valence shells if o Must be central nonmental atom Lewis Structure o Formula YQn Y P S Cl As Se Br Te I or Xe Q Halogen usually F or Oxygen Oxides of 3 period or higher have expanded shells which create a lesser formal Oxides of Heavier Elements charge Odd Electron Molecules Radicals Have an odd number of electrons Contain one unpaired electron Must be a central atom from odd number family group o N P S F Cl etc o 5A 7A etc Resonance Structures Variations of Lewis Structures which show alternative placements for double and triple bonds o DOES NOT CHANGE PLACEMENT OF ATOMS Geometry Shapes of Bonds Ball and stick diagrams show 3D placements of bonds VESPR o Predicts molecule shape from Lewis Structures o Rule 1 The molecule must be arranged so that the repulsions of electrons is minimal o Rule 2 Forces between electron pairs follow the order 6 Lone Pair Lone Pair repulsion Lone Pair Bonded Pair Bonded Pair Bonded Pair o Rule 3 If there is more than one central atom in a molecule the geometry of each of central atom must be determined separately To Determine Shape you must know o Steric Number SN SN of lone pairs on central atom of atoms bonded to the central atom SN 2 Linear SN 3 Trigonal Planar SN 4 Tetrahedral SN 5 Trigonal Bipyramidal SN 6 Octahedral o Shape is affected by Rule 2 Here are some trends in the naming If it helps 7

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KSU CHEM 1211 - Principles of Chemistry Review for Exam 2

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