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Ionization of Sodium Metal

Procedure

• Place a recrystallizing dish on an overhead projector.

• Pour water in the dish.

• Add a squirt of phenolphthalein and a squirt of soapy water so the sodium doesn't stick to the glass, swirl until mixed.

• Using tweezers, place a small piece of sodium metal in the dish and cover with the glass plate.

• The sodium will skim over the water surface leaving a pink trail.

• Repeat in another petri dish with potassium to show how reactivity of alkali metals increase down the periodic table. Dim the lights to show potassium aflame on the water's surface.

• Can start with lithium but it's really slow and boring.

Reactions

1. The sodium (and potassium) are oxidized:

Na (s) --> Na⁺ (aq) + e^-

2. Water is reduced:

2H₂O (l) + 2e^- -> H₂ (g) + 2OH^- (aq)