Alkali metals in water

[Schwann]

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Why do alkali metals react the most violently in cold water, more so than other metals?

 

[elementals]

As I understand it, alkali metals are generally very reactive due to how close they are to noble gas configuration, hence "wanting" to react in order to go to noble gas config. It's sort of like how halogens are also very reactive, but stuff in the middle (carbon, for example) is less so. All the alkali metals need to do is lose their single, unpaired electron and they're good to go. They're more reactive than other metals because other metals are all farther from noble gas config, and thus a little more stable where they are. Also, other metal can get stability from half-filled orbitals, etc.

If you drop a chunk of sodium into water, it'll blow the flask up 😉

 

[BerkReviewTeach]

Why do alkali metals react the most violently in cold water, more so than other metals?

Alkali metals have extremely low ionization energies (lowest of all elements), so they readily lose an electron to the only atom in solution capable of gaining that electron, H of water. The result is the formation of hydrogen gas, hydroxide, and heat.

M(s) + H2O(l) ---> M+(aq) + 1/2 H2(g) + OH-(aq) + heat

As any Hindenberg pilot will tell you, the heat and hydrogen gas combination is not such a good one, although they probably wouldn't care too much about the strong base that's formed. 😉