To understand how the principal energy levels fill with electrons in atoms beyond hydrogen

1
Objectives

1. To understand how the principal energy levels
   fill with electrons in atoms beyond hydrogen
2. To learn about valence electrons and core
   electrons
3. To learn about the electron configurations of
   atoms
4. 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
Classifying Electrons

• 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.

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 3s2 or 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
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 (?H) 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 ?H for the
  process X(g) e- X(g)-
•    ?H 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