Topics in this chapter
- Need for classification
- Mendeleev’s periodic table
- Modern periodic law
- Groups and periods
- Electronic configuration and position
- Atomic radius
- Ionisation tendency
- Electronegativity
- Metallic and non-metallic character
Key learning points
✓ The modern periodic table is arranged by increasing atomic number.
✓ Elements in the same group show similar valence-electron patterns.
✓ Atomic radius generally decreases across a period and increases down a group.
✓ Metallic character usually decreases across a period.
Multiple-choice questions
1. Modern periodic classification is based on:
- Atomic mass
- Atomic number
- Density
- Melting point
Answer: B — Atomic number
2. Elements in the same group have similar:
- Number of shells
- Valence-electron configuration
- Atomic mass
- Neutron number
Answer: B — Valence-electron configuration
3. Across a period atomic radius generally:
- Increases
- Decreases
- Remains fixed
- Becomes zero
Answer: B — Decreases
Very short-answer questions
- State the modern periodic law.
- How many periods are in the modern periodic table?
- What is periodicity?
Short-answer questions
- Explain the trend of atomic radius across a period and down a group.
- Relate electronic configuration to group and period.
Long-answer question
- Compare Mendeleev’s table with the modern periodic table and discuss major periodic trends.