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,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Periodic Trends,atomic radius,ionization energy,electron affinity,and electronegativity,be able to predict the order of elements for any given trend,Make a chart:,Trend,Definition,Picture of periodic trend,why?,practice,atomic radius,ionization energy,electron affinity,electro-negativity,Atomic Radius,Definition:,the distance from the nucleus to the edge of the electron cloud,found by taking half the distance between the nuclei of two bonded molecules,Br,2,=2.286 A(1.14 A),C-C=1.54 A(0.77 A),C-Br=1.91 A,examples,the trend!,atomic radius,increases,why?,ACROSS:,electrons added to the same energy level experience increasing attraction due to addition of protons,DOWN:,each period on the table adds a new energy level to the electron cloud,practice,sort the following from largest to smallest:,Ca,Mg,and Sr,Sr Ca Mg,K,Ga,Ca,K Ca Ga,Br,Rb,Kr,Rb Br Kr,ionization energy,Definition:,energy required to remove an electron from an atom,EX:Na+496 kJ,Na,+,+e,-,increase the more electrons are remove,EX:Na,+,+4562 kJ,Na,2+,+e,-,the trend,Ionization energy,increases,from left to right across a period,Ionization energy,decreases,going down a group,some are a little off the trend,Be:1s,2,2s,2,B:1s,2,2s,2,2p,1,n=2,Z,eff,=2,n=2,Z,eff,=3,1s,2,2s,2,1s,2,2s,2,2p,1,These 2e,-,do a better job of shielding the 2p,1,electron than they do of shielding each other,decrease in I,1,some are a little off the trend,N:1s,2,2s,2,2p,3,O:1s,2,2s,2,2p,4,n=2,Z,eff,=5,n=2,Z,eff,=3,1s,2,2s,2,1s,2,2s,2,2p,1,These 2e,-,repel one another,decrease in I,1,why?,Across:,Electrons are harder to remove from smaller atoms because they are close to the nucleus,DOWN:,Electrons are easier to remove from large atoms because they are farther from the nucleus,practice,sort the following from largest to smallest ionization energy:,Kr,He,Ar,He Ar Kr,Sb,Te,Sn,Te Sb Sn,K,Ca,Rb,Ca K Rb,Electron affinity,Definition:,energy change that happens with the addition of an electron to an atom,EX:X+,e,-,X,-,the trend,Electron affinity,increases,from left to right across a period,Electron affinity has,little change,going down a group but does,decrease,some are a little off the trend,Note that VA elements are less negative(dont attract electrons as well as),IVA elements,N:1s,2,2s,2,2p,3,n=2,Z,eff,=5,C:1s,2,2s,2,2p,2,n=2,Z,eff,=4,Adding,this electron,would increase the electron-electron repulsion and reduce the,electron-nucleus attraction for the added electron,less negative E,a,In general,atoms with filled or half-filled subshells have more positive electron,affinities than do elements on either side of them in the periodic table,some are a little off the trend,N:1s,2,2s,2,2p,3,O:1s,2,2s,2,2p,4,n=2,Z,eff,=5,n=2,Z,eff,=3,1s,2,2s,2,1s,2,2s,2,2p,1,These 2e,-,repel one another,decrease in I,1,why?,Across:,As nuclear charge increases it is more likely to attract electrons,DOWN:,Less energy released because electron is added at increasing distance fomr the nucleus,practice,sort the following from largest to smallest electron affinity:,Mn,K,and Ga,Ga Mn K,P,Sc,F,F P Sc,Electronegativity,Definition:,A measure of the ability of an atom in a chemical compound to attract electrons,the trend,electronegativity,increases,from left to right across a period,electronegativity,decreases,going down a group,why?,Across:,Shared electrons are closer to the nucleus in small atoms,DOWN:,Shared electrons are farther from the nucleus in large atoms,practice,sort the following from largest to smallest electronegativity:,Ca,Mg,and Sr,Mg Ca Sr,Te,S,Cl,Cl S Te,HW,Page 343:#84,86,98,Page 406:#20,
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