Alkali and alkaline earth metals

Groups

• Group IA: Li, Na, K, Rb, Cs. 1 electron in the outer shell.
• Group IIA: Be, Mg, Ca, Sr, Ba. 2 valence electrons.
• Alkali metals are strong reducing agents. Na and K are stored under kerosene. Li floats in kerosene, so it is stored under petroleum jelly.
• Going down the group, metallic character and reducing power increase. Their soluble hydroxides are strong alkalis.

Reaction with water

• 2Na + 2H₂O → 2NaOH + H₂↑.
• Ca + 2H₂O → Ca(OH)₂ + H₂↑.
• Mg reacts with water when heated (slowly under ordinary conditions).

Combustion products: Li → Li₂O, Na → Na₂O₂, K → KO₂.

Flame color

Metal	Flame color
Li	red
Na	Na gives a yellow flame
K	violet
Ca	Ca gives a brick-red flame
Sr	crimson
Ba	yellow-green

Important compounds

• Soda ash Na₂CO₃, baking soda NaHCO₃.
• Quicklime CaO, slaked lime Ca(OH)₂.
• Gypsum CaSO₄·2H₂O.
• Limewater turns cloudy with CO₂: Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O.
• CaCO₃ → CaO + CO₂ (heating).

Other information

• The hardness of water is due to Ca²⁺ and Mg²⁺ ions.
• Temporary hardness: Ca(HCO₃)₂. It disappears on boiling.
• Sodium is obtained by electrolysis of molten NaCl (Na and Cl₂).
• Li is the lightest metal.