Every alkali metal has just ONE electron in its outer shell. That's the key to everything.
Think of it this way:
- A full outer shell is the most stable electron configuration (like noble gases)
- It takes far less energy to lose 1 electron than to gain 7
- So the atom is in a lower energy state after losing that electron
Why reactivity INCREASES down the group:
- Going down, atoms get bigger (more shells)
- Outer electron is further from the nucleus
- Less attraction = easier to lose = more reactive
This deep dive covers Why Are Alkali Metals So Reactive? within Group 1: Alkali Metals for GCSE Chemistry. Revise Group 1: Alkali Metals in Atomic Structure for GCSE Chemistry with 22 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 3 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Group 1: Alkali Metals
How many electrons do alkali metals have in their outermost shell?
Explain why potassium is more reactive than sodium when it reacts with water.