Theory

To jump to a certain metal, click below:

Information that would be helpful to know before reading this section:

• The density of water is: 1 kg/m³
•  On the periodic table, the alkaline earth metals make up the leftmost column. As you go down the periodic table, the radius of the nuclei of the elements increases.  The greater the radius, the greater the distance from the outer electrons of the atom to its nucleus.  Therefore, it is easier for the atom to lose its outer electrons, and such atoms are less stable than atoms of small radii.  That explains why K, which is below Na, makes the most explosive reaction with water and why Li, which is above Na, makes the least explosive reaction with water; a K atom has a greater radius and more likely to lose outer electrons, making it less stable and more reactive.
• All of the reactions produced basic solutions (because of the hydroxides produced).
• All of the reactions were exothermic, as Jordan and Gabrielle can attest to (because of touching the water container immediately following the reactions). 

Reaction of Potassium With Water:

The K, which has a density of 856 kg/m³, skids quickly back and forth across the top of the water until the reaction is completed.  The K is able to stay above the water because the density of K is less than the density of H₂O. The reaction of K and H₂O takes less time compared to the length of time of the reactions of sodium or lithium and water. The result of the reaction of K and H₂O is a colorless solution of potassium hydroxide and hydrogen gas.  You can see in the following equation how K and H₂O produce KOH and H_2. 

2K(s) + 2H₂O => 2KOH(aq) + H₂(g)

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Reaction of Sodium With Water:

Upon the contact of Na with H₂O, the Na (density = 968 kg/m³) skids quickly across the surface of the H₂O, possibly propelled by bubbles of H₂ produced in the reaction (see our Analysis page).  The final products of the reaction are sodium hydroxide and hydrogen gas, as seen in the equation below.

2Na(s) + 2H₂O => 2NaOH(aq) + H₂(g)

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Reaction of Lithium With Water:

 The Li stayed on the surface of the water (density of Li = 535 kg/m³) and skidded around somewhat, producing large bubbles of H₂. The reaction also produced lithium hydroxide, as shown in the equation below.

2Li(s) + 2H₂O => 2LiOH(aq) + H₂(g)

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