Electron Arrangements and Atomic Properties: Periodic Table Trends

1. Objectives • To understand how the principal energy levels fill with electrons in atoms beyond hydrogen • To learn about valence electrons and core electrons • To learn about the electron configurations of atoms • To understand the general trends in properties in the periodic table

2. A. Electron Arrangements in the First 18 Atoms on the Periodic Table • H atom • Electron configuration – electron arrangement – 1s1 • Orbital diagram – orbital is represented as a box with a designation according to its sublevel. Contains arrow(s) to represent electrons (spin)

3. A. Electron Arrangements in the First 18 Atoms on the Periodic Table • He atom • Electron configuration – 1s2 • Orbital diagram

4. A. Electron Arrangements in the First 18 Atoms on the Periodic Table • Li atom • Electron configuration– 1s2 2s1 • Orbital diagram Write the electron configuration and orbital diagrams for Boron, Nitrogen, Fluorine and Argon

5. A. Electron Arrangements in the First 18 Atoms on the Periodic Table Write the full electron configuration of Neon and Sulfur Draw an orbital diagram for Magnesium and Chlorine

6. A. Electron Arrangements in the First 18 Atoms on the Periodic Table • Valence electrons – electrons in the outermost (highest) principal energy level of an atom • Core electrons – inner electrons • Elements with the same valence electron arrangement (same group) show very similar chemical behavior. • Classifying Electrons

7. B. Electron Configurations and the Periodic Table • Electron configurations for K through Kr

8. Using a Noble Gas Shorthand • We can abbreviate electron configurations by using the configuration of the previous noble gas to cover the first part of the list of orbitals • Mg is 1s2 2s2 2p6 3s2or [Ne] 3s2 • The noble gas portion is the equivalent to the group of core electrons • Use the Noble Gas shorthand to show the electron configurations of Carbon and Zirconium

9. Order of Filling of Orbitals Atoms fill their orbitals in the order of their energies:

10. B. Electron Configurations and the Periodic Table • Orbital filling and the periodic table

11. B. Electron Configurations and the Periodic Table

12. C. Atomic Properties and the Periodic Table Metals and Nonmetals • Metals tend to lose electrons to form positive ions. • Nonmetals tend to gain electrons to form negative ions.

13. (close to scale) C. Atomic Properties and the Periodic Table Atomic Size • Size tends to increase down a column. • Size tends to decrease across a row.

14. C. Atomic Properties and the Periodic Table Ionization Energies • Ionization Energy – energy (ΔH) required to remove an electron from an individual atom (gas) • Tends to decrease down a column • Tends to increase across a row • Changes in an opposite direction to atomic size

15. Ionization Energies

16. Electron Affinity • Electron Affinity is defined as ΔH for the process: X(g) + e- = X(g)- ΔH = Electron Affinity

17. Electronegativity • Ionization Energy and Electron Affinity are combined to give Electronegativity – a measure of how well atoms compete for electrons in a bond