Hooray for Mole Day!

Chemistry: Cute and cuddly (Photo: Mike E Talbot, CC-BY-SA)

I’m a mole! Hit me with chemistry! (Photo: Mike E Talbot, CC-BY-SA)


Chemistry enthusiasts all over the world will be celebrating Mole Day between 6:02 am and 6:03 pm today! 

But they aren’t commemorating the creature or undercover spies, benign tumours or even tasty sauces used in Mexican cuisine…

It’s Avogadro’s constant of course!


6.02214129 × 1023


This number tells us how many units (such as atoms or molecules) are present in one mole of a substance. This number is a constant meaning that it doesn’t matter which substance you choose, or whether that substance is a solid, liquid or a gas: one mole of it will contain this many units.

For example:

  • One mole of hydrogen contains 6.02214129 × 1023 atoms of hydrogen,
  • One mole of oxygen contains 6.02214129 × 1023  atoms of oxygen
  • And even when these two elements are combined to become water (H2O), one mole of water contains 6.02214129 × 1023 molecules of water.


To have moles explained through the medium of song, this video is well worth a watch! Thanks Bonnie Tyler.

Who first found Avogadro’s Constant?

In 1811, Italian scientist Amadeo Avogadro proposed that equal volumes of different gasses at the same temperature and pressure would contain the same number of particles. However, although this constant is named after Avogadro, it was over a Century later, in 1926, that French Physicist Jean Perrin won the Nobel Prize in Physics for his work in determining this value.


What makes today mole day?

Close inspection of Avogadro’s constant 6.02214129 × 1023 shows you the date and time. The end part shows x1023, giving us the date (23rd October) and the start of the number 6.02 gives us the time of day.

So there you have it today was clearly always supposed to be MOLE DAY! 


Happy Mole Day everyone!


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