CHAPTER 5 STUDY GUIDE JULY 6 2010 MORE ABOUT THE PERIODIC TABLE noble gases valence shells have completely filled valence electron shells chemically unreactive inert due to filled ATOMIC RADII A GROUP ELEMENTS ONLY atomic radii describes the relative sizes of atoms adding more protons left to right so the number of electrons determines atomic radii the reason atomic radii decrease across a period is due to a shielding effect periodic trends for atomic radii 4B Ti Zr Hf 7B 6B 5B Cr Mn V Nb Mo Tc Ta W Re 8B Fe Ru Os 8B Co Rh Ir 8B Ni Pd Pt 1B Cu Ag Au 2B Zn Cd Hg 3A B Al Ga In Tl 4A C Si Ge Sn Pb 5A N P As Sb Bi 6A O S Se Te Po smaller 8A He Ne Ar Kr Xe Rn 7A F Cl Br I At smaller larger 1A 2A H Li Be Na Mg Ca K Sr Rb Ba Cs Fr Ra larger example 3B Sc Y example going down column 6A O S Se Te going across period 3 Cl S P Si F S As Ga IONIZATION ENERGY example arrange these elements in order of increasing atomic radii Se S O Te arrange these elements in order of increasing atomic radii P Cl S Si arrange these elements in order of increasing atomic radii Ga F S As 1 CHAPTER 5 STUDY GUIDE JULY 6 2010 sometimes abbreviated as I E first ionization energy IE electron from an isolated gaseous atom to form a 1 ion when an atom loses its first electron like Mg atom g energy ion g e Na energy Na e 1 the minimum amount of energy required to remove the most loosely bound where Na has 1 unpaired electron with the electron configuration Ne 3s1 and Na has 0 unpaired electrons with the electron configuration Ne second ionization energy IE 2 the amount of energy required to remove the second electron from a Mg g 738 kJ mol Mg e gaseous 2 ion when an atom loses its second electron like Mg2 Mg Ne 3s2 738 kJ mol Mg Ne 3s1 1451 kJ mol Mg2 Ne ion energy ion2 e Mg 1451 kJ mol Mg2 e IE2 IE1 half filled and completely filled orbitals are more stable so it requires more energy to remove an electron and you destabilize the atom by adding an electron Be B 2s2 takes more energy to remove this electron 2s22p1 than to remove this electron atoms can have third fourth etc ionization energies periodic trends for ionization energy larger smaller 1A 2A H Li Be Na Mg Ca K Sr Rb Ba Cs Fr Ra smaller ionization energy 4B Ti Zr Hf 3B Sc Y 5B 6B 7B V Cr Mn Tc Nb Mo Ta W Re 8B Fe Ru Os 8B Co Rh Ir 8B Ni Pd Pt 1B Cu Ag Au 2B Zn Cd Hg 3A B Al Ga In Tl 4A C Si Ge Sn Pb 5A N P As Sb Bi 6A O S Se Te Po larger 8A He Ne Ar Kr Xe Rn 7A F Cl Br I At IE2 IE1 IE1 generally increases moving from the 1A elements to the 8A elements important exceptions at Be and Mg N and P etc due to filled and half filled subshells first ionization energies of some elements example arrange these elements in order of increasing first ionization energies Sr Be Ca Mg 2 CHAPTER 5 STUDY GUIDE JULY 6 2010 example arrange these elements in order of increasing first ionization energies Al Cl Na P example arrange these elements in order of increasing first ionization energies B O Be N Sr Ca Mg Be Na Al P Cl B Be O N ELECTRON AFFINITY electron affinity form an ion with a 1 charge sign conventions the amount of energy absorbed when an electron is added to an isolated gaseous atom to if electron affinity 0 then energy is absorbed if electron affinity 0 then energy is released electron affinity is essentially a measure of an atom s ability to form negative ions atom g e EA ion g Mg g e 231 kJ mol Mg g EA 231 kJ mol endothermic reaction Br g e Br g 323 kJ mol EA 323 kJ mol exothermic reaction periodic trends for electron affinity smaller larger 1A 2A H Li Be Na Mg Ca K Sr Rb Ba Cs Fr Ra larger 3B Sc Y 4B Ti Zr Hf 6B 7B 5B Cr Mn V Nb Mo Tc Ta W Re 8B Fe Ru Os 8B Co Rh Ir 8B Ni Pd Pt 1B Cu Ag Au 2B Zn Cd Hg 3A B Al Ga In Tl 4A C Si Ge Sn Pb 5A N P As Sb Bi 6A O S Se Te Po smaller 8A He Ne Ar Kr Xe Rn 7A F Cl Br I At exceptions for filled and half filled subshells Be N 2s2 filled 2p3 half filled EA 0 EA 0 electron affinity values of some elements example arrange these elements in order of increasing electron affinities Al Mg Si Na 3 Si Na Al Mg Na is bizarre in this instance otherwise would have been Si Al Na Mg CHAPTER 5 STUDY GUIDE JULY 6 2010 Na atom vs Na ion Na atom Na ion Ne 3s1 Ne e e IONIC RADII cations positive ions are always smaller than their respective neutral atoms cation positive ion radii decrease going from left to right across a period increasing nuclear charge attracts the electrons and decreases the ionic radius anions negative ions are always larger than their neutral atoms anion negative ion radii decrease going from left to right across a period increasing electron numbers in highly charged ions cause the electrons to repel and increase the ionic radius periodic trends for ionic radii 4B Ti Zr Hf 5B 6B 7B V Cr Mn Tc Nb Mo Ta W Re 8B Fe Ru Os 8B Co Rh Ir 8B Ni Pd Pt 1B Cu Ag Au 2B Zn Cd Hg 3A B Al Ga In Tl 4A C Si Ge Sn Pb 5A N P As Sb Bi 6A O S Se Te Po smaller 8A He Ne Ar Kr Xe Rn 7A F Cl Br I At smaller larger 1A H 2A Be Li Na Mg Ca K Sr Rb Ba Cs Fr Ra larger 3B Sc Y except it s more like this Na Mg2 Al3 N3 O2 F more electrons fighting for fewer protons causes repulsion 7N3 2 8O2 3 9F 10 e 10 e 10 e 7 p 8 p 9 p example example arrange these elements in order of decreasing ionic radii Ga K Ca K Ca2 Ga3 Cl S2 Br Se2 Cl period 3 S period 3 Br period 4 Se period 4 arrange these elements in order of increasing ionic radii Cl Se Br S ELECTRONEGATIVITY electronegativity chemically combined with another element a measure of the relative tendency of an atom to attract electrons to itself when the higher the number the more they are attracted to each other …