1. 1 CHEMISTRY 161 Chapter 8 Periodic Relationships Among the Elements ww.chem.hawaii.edu/Bil301/welcome.html

2. 2 Electron Configuration 1. Energetics 2. Pauli Principle 3. Hund’s Rule H  = E 

3. 3 cathode (-) anode (+) focus anode (+) metal Mosley’s Law cathode rays = [a(Z-b)] 2 e-e- frequency of emitted light atomic number (nuclear charge)

4. 4 Periodic Table of the Elements period groupgroup chemical reactivity - valence electrons ns 1 ns 2 ns 2 np 6 ns 2 (n-1)d x

5. 5 PERIODIC TRENDS 3. IONIZATION ENERGIES 4. ELECTRON AFFINITIES 1. ATOMIC RADIUS 2. IONIC RADIUS

6. 6 ATOMIC RADIUS

7. 7 MAIN GROUPS ATOMIC RADIUS

8. 8 1s, 2s, 3s 3s 2s 1s

9. 9 2p x, 3p x, 4p x 4p x 3p x 2p x

10. 10 ATOMIC RADIUS MAIN GROUPS ATOMIC RADIUS effective nuclear charge

11. 11 SCREENING AND PENETRATION PENETRATIONIs to get close to the nucleus SCREENING Is to block the view of other electrons of the nucleus

12. 12 SCREENING AND PENETRATION screening reduces the nuclear charge e-e- +Z e-e- core electrons versus valence electrons

13. 13

14. 14 SCREENING AND PENETRATION 1s close to the nucleus PENETRATES WELL‘SEES’ A CHARGE OF Z=2 EFFECTIVE NUCLEAR CHARGE Is 3p THE 3p DOES NOT SCREEN THE NUCLEUS THE 1s SCREENS THE NUCLEUS WELL

15. 15 SCREENING AND PENETRATION 3p far from the nucleus PENETRATES POORLY ‘SEES’ A CHARGE OF Z eff = Z – S = 2 – 1 = 1 Is 3p

16. 16 SCREENING AND PENETRATION Z eff = Z - S screening reduces the nuclear charge e-e- +Z e-e- Z eff approaches Z for an electron close to the core Z eff approaches +1 for an electron far from the core

17. 17 SCREENING AND PENETRATION Z eff INCREASES RADIUS DECREASES

18. 18 ATOMIC RADIUS d shell contraction d shell electrons screen Z ineffectively Z eff = 1 Z eff = 2.5 Z eff = 3.5 Z eff = 3.0 Z eff INCREASES

19. 19 ATOMIC RADIUS f shell contraction

20. 20 IONIC RADII IONIC RADIUS

21. 21 cations are smaller than their atoms anions are larger than their atoms Na is 186 pm and Na + is 95 pm F is 64 pm and F - is 133 pm same nuclear charge and repulsion among electrons increases radius one less electron electrons pulled in by nuclear charge O < O – < O 2– transition metals

22. 22

23. 23 EXAMPLES Which is bigger? Na or Rb Rb higher n, bigger orbitals K or Ca K poorer screening for Ca Ca or Ca 2+ Ca bigger than cation Br or Br - Br smaller than anion

24. 24 QUESTION The species F -, Na +,Mg 2+ have relative sizes in the order 1F - < Na + <Mg 2+ 2F - > Na + >Mg 2+ 3Na + >Mg 2+ > F - 4Na + =Mg 2+ = F - 5 Mg 2+ > Na + >F -

25. 25 QUESTION 1F - < Na + <Mg 2+ 2F - > Na + >Mg 2+ 3Na + >Mg 2+ > F - 4Na + =Mg 2+ = F - 5 Mg 2+ > Na + >F - Na + is 95 pm Mg 2+ is 66 pm F - is 133 pm ALL 1s 2 2s 2 2p 6 ALL are isoelectronic

26. 26 MAIN GROUPS ATOMIC RADIUS Summary ATOMIC RADIUS effective nuclear charge

27. 27 Homework Chapter 8 pages 289-303, problem sets