In the chemical shorthand ¹⁴C, the "14" represents the mass number of the carbon atom.

Here's a breakdown:

* ¹⁴C is the notation for a carbon isotope called carbon-14.

* Mass number represents the total number of protons and neutrons in an atom's nucleus.

* Carbon always has 6 protons (its atomic number).

* Therefore, ¹⁴C has 8 neutrons (14 - 6 = 8).

So, the "14" in ¹⁴C signifies that this carbon atom has a total of 14 protons and neutrons.