Alkali Metals: The Reactive Ones
Watch Group 1 metals explode in water.
What this lesson covers
Why it matters
Sodium skitters across the water like a hot coal, while potassium bursts into a lilac flame. These Group 1 metals react with startling vigour — and potassium can react explosively.
The idea in plain words
Balance potassium's equation — and notice it mirrors sodium's exactly: same products, same coefficients, just a more violent element.
Predict first
Why do alkali metals react so violently with water compared to other metals?
Alkali metals have a single valence electron that they lose extremely easily to form +1 ions, driving rapid displacement reactions.
- They have a low density and float
- They have one valence electron they lose easily — correct
- They are soft and can be cut with a knife
- Water is acidic and attacks metals
What you do
Add sodium first, then potassium. Observe the difference in vigor and flame color.
Check yourself
What gas is produced when sodium reacts with cold water?
The equation 2Na + 2H₂O → 2NaOH + H₂ shows hydrogen gas is released.
Why is the reaction of potassium with water more violent than sodium?
As you go down Group 1, atomic size increases, shielding increases, and the outer electron is held less tightly, making K more reactive than Na.
What is the chemical nature of the solution formed after sodium reacts with water?
The product is sodium hydroxide (NaOH), a strong base, making the solution alkaline.
- Oxygen
- Hydrogen — correct
- Nitrogen
- Potassium is larger and loses its valence electron more easily — correct
- Potassium is heavier than sodium
- Sodium forms a protective oxide layer instantly
- Acidic
- Neutral
- Alkaline — correct
- Saline