Lecture Notes: Reactivity Trends in the Periodic Table

Reactivity Overview

• Reactivity refers to how substances chemically interact.
• Indicators of reactivity: explosive reactions, gas production, color change, precipitate formation.

Periodic Table and Reactivity

• The periodic table helps explain differences in element reactivity.
• Key groups to understand: Noble Gases (Group 18) and Alkali Metals (Group 1).

Noble Gases (Group 18)

• Characteristics:
  • Full outer electron shell (8 valence electrons, 2 for helium).
  • Generally unreactive due to full valence shell.
• Example: Neon (10 electrons, full outer shell).

Alkali Metals (Group 1)

• Characteristics:
  • One valence electron.
  • Highly reactive, especially with water, oxygen, and acids.
• Example: Sodium
  • Has one electron in the outer shell, eager to lose for a full shell.
  • Reacts with chlorine to form table salt.

Reactivity Trends in Alkali Metals

• Reactivity increases as you move down Group 1.
• Atomic radius explanation:
  • Atomic Radius: Distance from nucleus center to outer shell.
  • Increases down a group as electron shells are added.
  • Example: Cesium is more reactive than sodium due to larger atomic radius.
  • Larger atomic radius = weaker attraction of valence electrons to nucleus.

Larger Alkali Metals Reactivity

• Larger alkali metals like rubidium and cesium lose valence electrons easily.
• Cesium, with the largest atom, is the most reactive in Group 1.

Trends in Alkaline Earth Metals (Group 2)

• Similar trends in atomic size and reactivity as in Group 1.
• Slightly less reactive than alkali metals.

Conclusion

• The periodic table is a valuable tool for understanding element interactions.
• Learning to read it reveals the underlying chemical properties and reactivity trends.