Period 3 and Redox Equilibria

Annotations:

• Na is in group 1 and Mg is in group 2 so when reacting with water Na loses 1 electron to form Na+ ion while Mg loses 2 electrons to form Mg 2+ ions. 
• It takes less energy to lose one electron than to lose 2 electrons so Na is more reactive than Mg.
• More energy (usually heat) is needed for Mg to react.

1. Sodium

   Annotations:

   • Reacts vigorously with cold water.
   • Forms a molten ball on the surface.
   • Fizzes
   • Produces H2 gas.
2. Magnesium

   Annotations:

   • Reacts very slowly with cold water 
   • Can't see any reaction
   • Forms a weak alkaline solution (pH 9 - 10).
   • The solution only produce a weak alkaline solution because Mg is not very soluble in water, so relatively few hydroxide ions are formed. 
   • Mg reacts much faster with steam (where there is more energy) to form Mg oxide.