Lecture Notes: Periodic Trends

Introduction

• Presenter: Andre from Med School EU
• Topic: Periodic Trends in Chemistry
• Purpose: Understanding how periodic trends explain the organization and properties of elements in the periodic table.

Overview of Periodic Trends

• Periodic Trends: Patterns within the periodic table that reflect element properties.
• Major Trends Discussed:
  • Atomic Radius
  • Ionization Energy
  • Electron Affinity
  • Metallic Character

Atomic Radius

• Definition: Distance from the nucleus to the outermost electron of an atom.
• Trend:
  • Increases from right to left.
  • Increases from top to bottom.
• Factors Affecting Atomic Radius:
  • Nuclear Charge: More protons mean more attraction and a smaller radius.
  • Comparison: Fluorine (9 protons) vs Be (4 protons); more protons pull electrons closer.
  • Shell Addition: More shells increase the atomic size moving down a group.

Ionization Energy

• Definition: Energy required to remove an electron from a neutral atom.
• Trend:
  • Increases from left to right.
  • Increases from bottom to top.
• Reasoning:
  • Outer electrons are easier to remove due to less attraction if far from the nucleus.
  • Sodium (11 protons) vs Chlorine (17 protons); chlorine's electrons are tightly bound.

Electron Affinity

• Definition: Energy released when an atom gains an electron.
• Trend: Similar to ionization energy.
  • Increases from left to right.
  • Increases from bottom to top.
• Factors:
  • Easier for atoms with higher nuclear charge to gain electrons.
  • Fluorine gains electrons more readily than sodium.

Metallic Character

• Definition: Level of reactivity of a metal.
• Trend:
  • Increases from right to left.
  • Increases from top to bottom.
• Characteristics:
  • Metals with fewer electrons in the outer shell are more reactive.
  • Metals like those in Group 1 are more reactive than those in Group 2.

Ions and Charges

• Concept: Atoms gain or lose electrons to become charged ions.
• Periodic Table Groups:
  • Group 1: Lose 1 electron, +1 charge.
  • Group 2: Lose 2 electrons, +2 charge.
  • Group 13 (Boron): Typically +3 charge.
  • Group 14 (Carbon): Can gain or lose 4 electrons.
  • Group 15 (Nitrogen): Gain 3 electrons, -3 charge.
  • Group 16 (Oxygen): Gain 2 electrons, -2 charge.
  • Group 17 (Fluorine): Gain 1 electron, -1 charge.
  • Noble Gases: Full octet, no charge.

Conclusion

• Next Topic: Chemical bonds.
• Advice: Memorize ion charges and periodic trends for better understanding.