Periodic Properties of Elements Chapter 7 part I

Periodic trends in Orbitals

Periodic Trends in Electron Orbitals

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

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

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

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.

Periodic Trends in Ionization Energy

Questions Which of these atoms has the largest 1st ionization energy? 2nd? Which has the smallest? Why? 1s22s22p6 1s22s22p63s1 1s22s22p63s2

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.

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

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.

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?

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.

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

Other trends: Metallic Character