1. Which thinker first described the idea of four classical elements (earth, water, air, fire)?

2. Who proposed the first modern atomic theory that atoms are indivisible units with different masses?

3. What important scientific tool did Dmitri Mendeleev create in 1869?

4. Which discovery showed that atoms are made of smaller particles?

5. Which of the following is a noble gas commonly used in lighting?

6. In 1–2 sentences, explain how Mendeleev used gaps in his table to help predict new elements.

7. Name two elements and give one important modern use for each (e.g. silicon — ___________ ; copper — ___________ ).

8. Describe briefly how the discovery of subatomic particles (electrons, protons, neutrons) changed our definition of an element.

9. Match each element (left) with a common use (right). Draw lines between matching items.

10. Creative task: Draw a simple timeline in the box below showing these milestones: classical four elements → Lavoisier (element defined) → Dalton (atomic theory) → Mendeleev (periodic table) → discovery of electron.