According to the Notting Hill and Ealing High School, the reaction of caesium $\ce{Cs}$ with water $\ce{H2O}$ gives the following equation, $$\ce{2Cs (s) + 2H2O (l) → 2CsOH (aq) + H2 (g)},$$ producing caesium hydroxide $\ce{CsOH}$ and hydrogen $\ce{H2}$, thus it's not hard to understand why is the reaction so violent.

But I don't really understand the reaction. Is this a single displacement reaction?

If so, why does the water break so fast into $\ce{H2}$ and $\ce{OH}$ ?

Is this related to caesium's weak electronegativity? ($0.79$ on the Pauling scale)

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    $\begingroup$ $\ce{Cs}$ donates a single electron to a hydrogen of water and forms $\ce{Cs+,}$ $\ce{H^\bullet}$ and $\ce{OH-}$. And then, two hydrogen atoms combine to form $\ce{H2}$ gas. $\endgroup$ – Apoorv Potnis Feb 7 '18 at 12:13
  • $\begingroup$ So this is a redox reaction? The Cs is reducted by the hydrogen? $\endgroup$ – americium1997 Feb 7 '18 at 12:19
  • $\begingroup$ The oxidation number of $\ce{Cs}$ is increased from $0$ to $+1$. So, I think $\ce{Cs}$ is oxidised. s-block metals generally function as reducing agents. $\endgroup$ – Apoorv Potnis Feb 7 '18 at 12:24

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