Which element in the list is the most reactive?

C

Ba

S

Cs

Cs

Explanation:

This element is the farthest right, and lowest meaning that the reactivity of it is very high.

1. valence electrons and electronegativity

2. Both reactivity and electronegativity decrease down a group.

3. Electronegativity decreases down a group, and reactivity increases down a group.

4. The number of valence electrons increases from left to right.

5. Cs

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