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sodium catches fire and explodes in water chemistry cartoonWhat causes sodium to explode in water?

  • Happy Valentine's Day! Here's a quick summary of the romantic relationship between sodium and water...
  • Sodium is an alkali metal which is very reactive because it has an unstable electron configuration.

Atoms like to fulfil the rule of octet

  • The rule of octet states that generally, atoms like to have eight valence electrons in the outermost shell but sodium has only one valence electron. This causes it to become reactive and have a strong tendency to give up the single electron.
  • Basically, when sodium is added to water, sodium reacts vigorously with water.
  • The exothermic reaction produces sodium hydroxide and hydrogen gas. (Read here for more detailed explanation of sodium and water reaction).
  • Hydrogen is flammable and ignites itself to cause an explosion. This is the classic explanation of why sodium explodes in water but recently a better explanation has been found.

What causes sodium to catc hfire in water - chemistry high school

Why Sodium Really Explode In Water - The New Theory

  • Sodium's explosion in water has long been a mystery. Thanks to high speed super-fast video footage, scientists can now understand better sodium's energetic reaction with water.
  • "Spikes of metal could be seen shooting very rapidly out into the water, within less than half a millisecond of the two surfaces coming into contact. And there was a flash of a bluish purple colour at about the same time." ~ 
  • When sodium hits water, sodium's outermost electrons all leave at once due to low ionization energy. (Ionization energy is the energy required to remove an electron from an atom).
  • The electron departure leaves behind the metal cluster full of positively charged ions which then repel each other and blast outward in tiny spikes in a reaction called Coulomb explosion.
  • The observation shows sodium explodes very quickly in water - within a fraction of a millisecond.