Condensed Electron Configurations Lecture

Introduction

• Focus on learning to write condensed electron configurations.
• Includes examples and practice exercises.

Understanding Electron Configurations

• Bromine:
  • Atomic number: 35 (protons = electrons).
  • Full electron configuration can be condensed using the noble gas before it (Argon, with 18 electrons).
  • Condensed form: [Ar] 3d10 4s2 4p5.

Steps to Write Condensed Electron Configurations

1. Identify the element and its atomic number.
2. Find the noble gas before the element in the periodic table.
3. Use the noble gas as the core and add the remaining electrons.

Examples

Lithium

• Atomic number: 3.
• Noble gas before Lithium: Helium (1s2).
• Condensed form: [He] 2s1.

Carbon

• Atomic number: 6.
• Use Helium as the noble gas core.
• Condensed form: [He] 2s2 2p2.

Calcium

• Atomic number: 20.
• Noble gas before: Argon (18 electrons).
• Condensed form: [Ar] 4s2.

Calcium Ion (Ca²⁺)

• Has lost 2 electrons (20 protons remain, electrons = 18).
• Electron configuration same as Argon: [Ar].
• For clarity, write [Ar] 4s0 to indicate loss of valence electrons.

Iodine

• Atomic number: 53.
• Noble gas before: Krypton (36 electrons).
• Condensed form: [Kr] 4d10 5s2 5p5.
• Note: D orbitals (4d10) are considered filled and do not usually participate in reactions.

Barium

• Atomic number: 56.
• Noble gas before: Xenon (54 electrons).
• Condensed form: [Xe] 6s2.
• Contains two valence electrons.

Additional Notes

• Condensed configurations simplify the expression of electron arrangements.
• Highlight valence electrons, useful for understanding chemical reactivity.
• Special cases like ions require adjustment by adding or removing electrons from the configuration.

Conclusion

• Condensed electron configurations help visualize valence electrons and save time.
• This knowledge facilitates understanding of chemical properties and reactivity.

Lecture by Dr. B on writing condensed electron configurations.