How does the reactivity change down Group 1 elements, and why?
The reactivity increases. Group 1 are the alkali metals so they react by losing their valence electrons. Caesium is more reactive because it gives up its electrons more readily. It has more inner shells so its valence electrons are further from the positive nucleus and feel less attraction.
EH
Related Chemistry A Level answers
All answers ▸How does ionisation energy vary across a period in the periodic table?
What is an acid and what is the difference between and strong and weak acid
How would you check for halides within a compound and differentiate between them?
How do you work out the oxidation number of a atom in a compound?