1. Periodic Properties of Elements Chapter 7 part I

2. Periodic trends in Orbitals

3. Periodic Trends in Electron Orbitals

4. Exceptions to the rules  Chromium and Copper do not follow the expected electron configuration.  Cr is expected to be [Ar]4s 2 3d 4  Cu is expected to be [Ar]4s 2 3d 9

5. Ionization energy  The energy required to remove one electron from a gaseous element or ion.

6. Ionization Energy (kJ/mol) 1st2nd3rd4th5th Li520729811815 Be8991757184921006 B801242736602502632827 C108623534620622237830

7. Ionization energy  First ionization energy is the energy required to remove the highest energy electron.  As the number of protons increase, generally it is more difficult to remove an electron until a shell is completed.

8. Periodic Trends in Ionization Energy

9. Questions  Which of these atoms has the largest 1st ionization energy?  2nd?  Which has the smallest?  Why?  1s 2 2s 2 2p 6  1s 2 2s 2 2p 6 3s 1  1s 2 2s 2 2p 6 3s 2

10. Solution  Ne (1s 2 2s 2 2p 6 ) has the highest 1st ionization energy as it has a complete s p shell.  Na (1s 2 2s 2 2p 6 3s 1 ) has the lowest 1st due to shielding.  2nd: Highest Na+(1s 2 2s 2 2p 6 )  2nd: Lowest Mg+(1s 2 2s 2 2p 6 3s 1 ) due to shielding.  What is shielding?  Shielding is the description of a complete electron shell (core electrons) and its “neutralizing” of the positive charge of the nucleus. This causes outer shell electrons to be bound less strongly to the atom.

11. Electron Affinity  The energy change associated with the addition of an electron to an atom in its gaseous state.

12. Electron Affinity  Is often referred to as the energy released when an atom accepts an electron.  The more negative the number the more energy released.

14. Atomic radius  These values are obtained by measuring the distance between atoms in chemical compounds.  These values may be smaller than the 90% of the electron density. Why?

15. Atomic radius of ions  When electrons are added to an atom one would expect an increase in the radius.  One would also expect a decrease in radius when an electron is removed.

17. Atomic radius  But why does the radius of the atom decrease with each increase in atomic number???

18. Other trends: Metallic Character