Observe. Find the pattern. Predict the element no teacher would ever hand you.
Before you beginBackground
Every element in Group 1 of the periodic table has exactly one valence electron — a single electron in its outermost shell. When an alkali metal touches water, it gives that electron away, producing hydrogen gas and a metal hydroxide. The reaction releases heat. How violently it happens depends on how easily the atom loses that electron.
As you move down the group, atoms get bigger. The valence electron sits farther from the nucleus, shielded by more inner shells, so the nucleus holds it more weakly.
3
Li
Lithium
6.94
11
Na
Sodium
22.99
19
K
Potassium
39.10
37
Rb
Rubidium
85.47
55
Cs
Cesium
132.91
You will test the three outlined in gold. Cesium is your prediction target.
Why this lab is virtual: real alkali metals are stored under oil because they react with the moisture in air. Potassium can ignite on contact with water, and cesium reactions are violent enough to shatter glassware. No school lab performs these reactions live — which is exactly why chemists need predictive models instead of trial and error.
Part 1Observe the Reactions
At each station, press Drop metal into water and watch the full reaction. Run it as many times as you need. Record what you see — be specific: movement, speed, gas, flame, sound, how long it lasts.
LiLithium — Station 1Atomic number 3 · 2 electron shells
Runs: 0
Observations ✔ simulation completed
What did the metal do? (movement, surface behavior, gas)
NaSodium — Station 2Atomic number 11 · 3 electron shells
Runs: 0
Observations ✔ simulation completed
What did the metal do? How is it different from lithium?
Estimated reaction intensity (1–10) and why
KPotassium — Station 3Atomic number 19 · 4 electron shells
Runs: 0
Observations ✔ simulation completed
What did the metal do? What appeared that you did NOT see with Li or Na?
Estimated reaction intensity (1–10) and why
Part 2Find the Pattern
Complete the table using your observations and the atomic data given.
Metal
Electron shells
Your intensity rating & key evidence
How easily does it lose its valence electron? (your inference)
Li
2
Na
3
K
4
State the trend in one sentence: as you move down Group 1, reactivity ________ because ________.
Part 3Predict: Cesium
Cesium sits two rows below potassium — atomic number 55, with 6 electron shells. Its valence electron is the farthest from the nucleus of any stable element. Before you may run the cesium test, you must commit to a written prediction.
Prediction — Describe exactly what you expect to happen when cesium hits water. Be specific about speed, gas, flame, and intensity compared to potassium.
Reasoning — Justify your prediction using valence electrons, atomic size, and the group trend. (This is the part that makes it science instead of a guess.)
🔒 The cesium station unlocks when both boxes above contain a real prediction (a few full sentences each).
Part 4The Cesium Test
CsCesium — Restricted StationAtomic number 55 · 6 electron shells
Runs: 0
Locked — complete Part 3 first.
Results ✔ simulation completed
What actually happened?
Compare to your prediction. What did you get right? What surprised you?
Part 5Revise and Explain
1. Write a revised, final explanation of WHY reactivity increases down Group 1. Use the words valence electron, nucleus, shells, and attraction.
2. Francium (Fr) sits one row below cesium, but scientists have never filmed it reacting with water — only a few atoms exist at a time. Using your model, what would you tell them to expect?
3. Why are predictive models like the one you just built more useful to chemists than simply testing every element?
Finished? Check that your name is at the top and every box has an answer, then print this page and choose Save as PDF. Upload the PDF to the Schoology assignment.