Here's why:

* More reactive metals like potassium, sodium, and magnesium are higher up in the series. They readily react with acids and displace other metals from their compounds.

* Less reactive metals like silver, gold, and platinum are lower down. They are less likely to react with acids and are not easily displaced.

Copper is considered a moderately reactive metal. It reacts with strong oxidizing acids like nitric acid but not with dilute acids like hydrochloric acid.

Here's a simplified reactivity series for reference:

1. Potassium

2. Sodium

3. Calcium

4. Magnesium

5. Aluminum

6. Zinc

7. Iron

8. Tin

9. Lead

10. Copper

11. Mercury

12. Silver

13. Gold

14. Platinum