📚 Part 1: Understanding the Trends

Introduction: Group 1 (alkali metals) and Group 7 (halogens) show clear patterns in their physical and chemical properties as you move down the group. These trends are explained by changes in electronic structure.

Key Definitions:

• Atomic radius: The distance from the nucleus to the outermost electrons

• Ionisation energy: Energy needed to remove an electron from an atom

• Electronegativity: The ability of an atom to attract electrons in a bond

1. Which statement about Group 1 elements is correct as you go down the group?

Atomic radius decreases

Ionisation energy increases

Reactivity increases

Melting point increases

2. For Group 7 elements going down the group, which properties increase?

Atomic radius

Boiling point

Electronegativity

Number of electron shells

3. Complete the sentences about electronic structure:

Group 1 elements have _______ electron(s) in their outer shell.

Group 7 elements have _______ electrons in their outer shell.

As you go down a group, the number of electron shells _____________.

4. Why does reactivity increase down Group 1?

More protons in the nucleus

Outer electron is further from nucleus and easier to lose

Atoms get smaller

More neutrons are present

✏️ Part 2: Extended Response & Analysis

5. Explain why the melting points of Group 1 elements decrease as you go down the group. Include reference to atomic structure in your answer.

6. Compare and contrast the trend in reactivity for Group 1 and Group 7 elements. Explain why these trends are opposite.

7. Think & Debate: Francium is the most reactive Group 1 element, but it's extremely rare and radioactive. If you could safely study francium, predict three properties it would have and justify your predictions using periodic trends.

🎯 Part 3: Application & Recap

8. A student claims: "Chlorine is more reactive than iodine because it has more electrons." Evaluate this statement and provide a better explanation for the difference in reactivity.

9. Interesting Fact: Caesium metal melts at just 28.4°C and can melt in your hand! Use your knowledge of Group 1 trends to explain why caesium has such a low melting point compared to lithium (180.5°C).

10. Match the element to its correct position trend:

Li → Na → K → Rb → Cs

F → Cl → Br → I → At

Atomic radius: _____________ down both groups

Ionisation energy: _____________ down both groups

Group 1 reactivity: _____________ down the group

Group 7 reactivity: _____________ down the group

11. Challenge Question: Explain why the first ionisation energy of potassium (419 kJ/mol) is much lower than that of chlorine (1251 kJ/mol), even though they are in the same period.