Periodic Trends - Chemical Principles - Lecture Slides, Slides of Chemical Principles

Download Periodic Trends - Chemical Principles - Lecture Slides and more Slides Chemical Principles in PDF only on Docsity! Periodic Trends Periodic Trends • Ionization Energy, • Electron Affinity, • Radii docsity.com Periodic Trends • The valence electron structure of atoms can be used to explain various properties of atoms. • In general, properties correlate down a group of elements. • A warning: such discussions are by nature very generalized…exceptions do occur. docsity.com Periodic Trends: Ionization • One can perform multiple ionizations: Al(g) Al+(g) + e- I1 = 580 kJ/mol first Al+(g) Al2+(g) + e- I2 = 1815 kJ/mol second Al2+(g) Al3+(g) + e- I3 = 2740 kJ/mol third Al3+(g) Al4+(g) + e- I4 = 11,600 kJ/mol fourth docsity.com Which reaction represents the ionization of F? A. 1s22s22p5 B. 1s22s22p5 1s22s22p6 1s22s22p43s1 C. 1s22s22p5 1s22s22p4 D. 1s22s22p5 1s22s12p6 docsity.com Periodic Trends: Ionization • First Ionization Potentials: Column 1 Column 8 docsity.com Which atom would you expect to have the lowest ionization energy? A. 1s22s22p3 B. 1s22s22p63s23p5 C. 1s22s22p63s23p64s2 D. 1s22s22p63s23p64s23d104p65s1 docsity.com Periodic Trends: Electron Affinity • Electron Affinity: the energy change associated with the addition of an electron to a gaseous atom. +Z Z- +Z (Z+1)- e- Energy docsity.com Periodic Trends: Electron Affinity • We will stick with our thermodynamic definition, with energy released being a negative quantity. Wow! docsity.com Periodic Trends: Electron Affinity • Why is EA so great for the halogens? F(g) + e- F-(g) EA = -327.8 kJ/mol 1s22s22p5 1s22s22p6 [Ne] • Why is EA so poor for nitrogen? N(g) + e- N-(g) EA > 0 (unstable) 1s22s22p3 1s22s22p4 (e- must go into occupied orbital) docsity.com Periodic Trends: Electron Affinity • How do these arguments do for O? O(g) + e- O-(g) EA = -140 kJ/mol 1s22s22p4 1s22s22p5 • What about the second EA for O? O-(g) + e- O2-(g) EA > 0 (unstable) 1s22s22p5 1s22s22p6 [Ne] configuration, but electron repulsion is just too great. Bigger Z+ overcomes e- repulsion. docsity.com Which diagram indicates the evolution in electron affinity from high affinity to low affinity? docsity.com