Practice question · Multiple choice
Moving down the alkali metals (Li → Na → K → Rb), the atoms get bigger, yet they give up their outer electron more easily. Why?
Hints
- Two effects fight: nuclear charge grows, but so do distance and the number of shielding electron shells. Which wins for the outermost electron?
- Coulomb attraction dies off with distance, and each filled inner shell cancels roughly one unit of nuclear charge.
Show the answer
D. The outer electron is farther out and more screened
Why
Distance plus shielding beat the extra protons: the valence electron of Rb feels roughly the same effective charge as Li’s but from much farther away. That is why reactivity of alkali metals increases downward, cesium ignites on water while lithium merely fizzes.
Practise Chemical periodicity
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