# Which alkali metal element is the most reactive?

Jan 28, 2017

$\text{Caesium, francium...................?}$

#### Explanation:

Both of these metals are the heaviest alkali metals. The higher molecular mass metals are not available in quantity, and are quite expensive. Sodium and lithium are generally available in a lab. You can destroy sodium with ethanol:

$N a + {H}_{3} C - C {H}_{2} O H \rightarrow {H}_{3} C - C {H}_{2} {O}^{-} N {a}^{+} + \frac{1}{2} {H}_{2} \left(g\right) \uparrow$

The same reaction with potassium will ignite the ethanol. Sodium potassium alloy, which is approximately $N a {K}_{2.8}$ in composition, is a liquidus (and even more reactive than potassium), and for this reason is commonly used to dry low boiling point solvents (i.e. diethyl ether, pentane, and hexanes). There are safe means to decompose these metals, but they require care and experience.