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]4s23d4
Cu is expected to be [Ar]4s23d9

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

6. Ionization Energy (kJ/mol)
1st
2nd
3rd
4th
5th Li
520
7298
11815 Be
899
1757
1849
21006 B
801
2427
3660
25026
32827 C
1086
2353
4620
6222
37830

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?
1s22s22p6
1s22s22p63s1
1s22s22p63s2

10. Solution
Ne (1s22s22p6) has the highest 1st ionization energy as it has a complete s p shell.
Na (1s22s22p63s1) has the lowest 1st due to shielding.
2nd: Highest Na+(1s22s22p6)
2nd: Lowest Mg+(1s22s22p63s1) 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