Element Properties and Prediction

Use chemical periodicity to predict properties of elements in a group. Deduce unknown elements' nature and position from given properties.

Group 1 (Alkali Metals)

• Characteristics: Relatively soft metals
• Trends down the group:
  • Decreasing melting point
  • Increasing density
  • Increasing reactivity

Group 7 (Halogens)

• Characteristics: Diatomic non-metals
• Trends down the group:
  • Increasing density
  • Decreasing reactivity
• Appearances at room temperature:
  • Fluorine: Pale yellow gas
  • Chlorine: Yellow-green gas
  • Bromine: Red-brown liquid
  • Iodine: Grey-black solid
• Reactions:
  • Displacement reactions with halide ions
  • Act as reducing agents

Hydrogen Halides

Analyze relative thermal stabilities. Explain in terms of bond strengths.

Transition Elements

• Characteristics:
  • High densities
  • High melting points
  • Variable oxidation numbers
  • Form colored compounds
  • Act as catalysts (e.g., Haber process, catalytic converters)

Group 18 (Noble Gases)

Characteristics: Unreactive monoatomic gases. Explain unreactivity in terms of electronic configuration.

Metals vs. Non-metals

• Compare general physical properties:
  • Thermal conductivity
  • Electrical conductivity
  • Malleability and ductility
  • Melting and boiling points

Periodic Table Structure

• Elements arranged by increasing atomic number
• Based on Periodic Law: Properties repeat periodically
• 7 periods (horizontal rows)
• 18 groups (vertical columns)

Blocks in the Periodic Table

• s-block: Groups 1 and 2
• p-block: Groups 13 to 18 (except He)
• d-block: Transition elements
• f-block: Lanthanides and actinides