The Metals That Hate Water
📖 The Metals That Hate Water
Alkali metals hold their outer electron like a hot potato — they can't wait to get rid of it! With only 1 electron in their outer shell, losing it gives the atom a stable full-shell configuration underneath. Now imagine the nucleus as a magnet and the outer electron as a paperclip. In lithium, the paperclip is close — the magnet grips it firmly. In potassium, the paperclip is three times further away, with inner electron shells blocking the pull — it escapes much more easily. The further away the electron sits, the less firmly the nucleus holds it, and the more readily the atom reacts.
Every alkali metal has just ONE electron in its outer shell. That's the key to everything.
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🧠 Memory Aids
"LiNaK RbCs Fr" — Li-Na-K-Rb-Cs-Fr — the Group 1 elements in order. "Little Naughty Kids Roam Cities Freely" helps recall: Lithium, Sodium (Na), Potassium (K), Rubidium, Caesium, Francium.
Reactivity trend: "Bigger = Looser = More Reactive" — as atoms get bigger down the group, the outer electron is held more loosely, so the element is more reactive.
Water reaction product: "Alkali metal + Water = HOH (metal Hydroxide + Hydrogen)" — always produces a hydroxide and hydrogen gas.
Quick Check: Explain why potassium is more reactive than lithium when reacting with water.
Potassium has more electron shells than lithium, so its outer electron is further from the nucleus. There is also greater electron shielding. This means the electrostatic attraction between the nucleus and the outer electron is weaker, so the electron is lost more easily, making potassium more reactive.
Now try it yourself
Quiz · Question 1 of 22
How many electrons do alkali metals have in their outermost shell?
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This topic in real past papers
Every real exam question we've found on group 1: alkali metals, with a full worked answer.