Mole

Number of atoms in 12g or the carbon-12 isotope. (About a cube of sugar in quantity.)
About 6.022e23 ⚛️s
Or precisely: 602,214,076,000,000,000,000,000 ⚛️s

A unitless number.
Can be used for counting parts that are not atoms too.

External links

• https://en.wikipedia.org/wiki/Mole_(unit)
• https://en.wikipedia.org/wiki/Avogadro_constant
• https://en.wikipedia.org/wiki/2019_revision_of_the_SI

Side-note: Two ways to put an atom in text: ⚛️ & ⚛