IGCSE Chemistry 0620 — Topic 8
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Periodic Table

Groups I, VII, VIII, Transition Metals & Trends

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Learning Objectives

Understand periodic table organization

Identify trends across periods and down groups

Predict element properties from position

Understand Group I alkali metals

Understand Group VII halogens

Know Group VIII noble gases

Recognize transition metals

Periodic Table Organization

The periodic table is organized by:

• Periods (rows): Number of electron shells increases down
• Groups (columns): Same number of valence electrons
• Elements with similar properties in same group

Trends Across a Period

As you move LEFT to RIGHT across a period:

• Atomic radius DECREASES (more protons pull electrons closer)
• Ionization energy INCREASES (harder to remove electrons)
• Electronegativity INCREASES (atoms pull electrons harder)
• Metallic character DECREASES (metals → nonmetals)

Trends Down a Group

As you move DOWN a group:

• Atomic radius INCREASES (more electron shells)
• Ionization energy DECREASES (valence electrons farther away)
• Electronegativity DECREASES (larger atoms hold electrons less tightly)
• Metallic character INCREASES (nonmetals → metals)
• Reactivity changes (increases for Group I, decreases for Group VII)

Group I: Alkali Metals

Structure

  • 1 valence electron
  • Outer electron easily lost
  • Form +1 ions
  • Soft, low melting point

Properties

  • Highly reactive
  • React with water: 2Na + 2H₂O → 2NaOH + H₂
  • Reactivity increases down group
  • Stored under oil (prevent reaction with O₂/H₂O)

Group I Reactions with Water

2M + 2H₂O → 2MOH + H₂

Reactivity order: Cs > Rb > K > Na > Li

Produces alkaline solution (hydroxide)

Vigorous reaction with increasing reactivity

Group VII: Halogens

Structure

  • 7 valence electrons
  • Need 1 more electron
  • Form -1 ions
  • Nonmetallic

Properties

  • Very reactive
  • Displace less reactive halogens
  • Reactivity decreases down group
  • F₂ > Cl₂ > Br₂ > I₂

Halogen Displacement Reactions

More reactive halogen displaces less reactive

Cl₂ + 2KBr → 2KCl + Br₂

Br₂ + 2KI → 2KBr + I₂

F₂ displaces all others, I₂ displaces none

Group VIII: Noble Gases

8 valence electrons (except He: 2) = full outer shell = stable

• UNREACTIVE (inert) - do not form compounds
• Monatomic (single atoms)
• Low melting/boiling points
• Examples: He, Ne, Ar, Kr, Xe, Rn

Transition Metals

Located in middle block (Groups 3-12)

Multiple oxidation states (variable charge)

Hard, strong, dense metals

Good conductors of heat and electricity

Examples: Fe, Cu, Zn, Cr

Lesson Summary

Periodic table organized by groups (columns) and periods (rows)

Properties change predictably across and down table

Group I: Soft, reactive metals (increasing down)

Group VII: Reactive nonmetals (decreasing down)

Group VIII: Unreactive noble gases (full valence shell)

Transition metals: Hard, strong, multiple oxidation states

Trends help predict unknown element properties

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