Chapter 08 - Electron Configuration and Chemical Periodi(2)

Chapter 08 - Electron Configuration and Chemical Periodi(2)...

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Unformatted text preview: 8-1Chapter 8Chapter 8Electron Configuration and Electron Configuration and Chemical Periodicity IIChemical Periodicity II8-2The Modern Periodic TableThe Modern Periodic TableNoble GasesPeriodsAlkali MetalsAlkaline Earth MetalsGroupsOxygen Family8-3Similar Reactivities Within a GroupSimilar Reactivities Within a GroupElements in the same group have similar outer electron configurations and therefore similar chemical propertiesOrbitals are filled in order of increasing energy, which leads to periodically recurring outer electron configurationsand periodically recurring chemical properties8-4Trends in Atomic PropertiesTrends in Atomic PropertiesAll physical and chemical behavior of the elements is based on the electron configurations of their atomsAtomic SizeIonization EnergyElectron AffinityChemical reactivity8-5Atomic Radii of the Main-group and Transition Atomic Radii of the Main-group and Transition ElementsElementsIncrease in sizeDecrease in sizeAtomic Radius of main group and transition group elements in picometers (10-12m)Smallest atom: F, 31 pmLargest atom: Cs, 265 pm; Fr, 270 pm (very rare element, see Chpt. 14)HHe8-6Periodicity of Atomic RadiusPeriodicity of Atomic Radius8-7Trends in Atomic PropertiesTrends in Atomic PropertiesAtomic SizeAtomic SizeAtomic SizeAtomic SizeIncrease in n: outer electrons spend more time farther away from the nucleus, thus atom is largerChanges in effective nuclear charge, Zeff : increase in Zeffresults in larger pull on the electrons, thus atom is smallerIn group: ndominates and size increases, because of shielding effect of inner electronsAcross period: Zeff +dominates because increase in number of protons in nucleus and no change in shielding results in larger atom size8-8Trends in Atomic PropertiesTrends in Atomic PropertiesIonization EnergyIonization EnergyIonization EnergyIonization EnergyEnergy (in kJ) required for the removal of 1 mol of electrons from 1 mol of atoms or ions in the gas phaseIonization energy decreases down a group(larger atomic size)Exception Group 3A after Al (effect of transition elements)Ionization energy generally increases across a periodZeffincreases, atomic size decreasesIonization energy is always positive: energy flows into the systemFirst ionization energy IE1removes 1stelectronatom (g) ion+(g) + e-E = IE1> 0Second ionization energy IE2removes 2ndelectron, etc.ion+(g) ion2+(g) + e-E = IE2> IE1> 0Elements with low IE1form cations(loose electrons)Elements with high IE1form anions(capture electrons)Dip for O (between N and F)O has 2p4electrons increase in electron repulsion removal of 1 electron relieves repulsion8-9Periodicity of First Ionization Energy (IEPeriodicity of First Ionization Energy (IE1))8-10First Ionization Energies of the Main-group Elements....
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This note was uploaded on 04/13/2008 for the course CHEM 1311 taught by Professor Baishakhidas,ms. during the Spring '08 term at Alamo Colleges.

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Chapter 08 - Electron Configuration and Chemical Periodi(2)...

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