# Meaning of m2 in the symbol for an isotope of an element

What does the notation $^{197\mathrm{m}2}\ce{Pb}$ mean? Specifically, the '$\mathrm{m}$2' part.

I've found this and it appears to have something to do with charge distribution. The original notation was found here.

• – Loong Jan 21 '17 at 18:51

The letter $m$ is sometimes appended after the mass number to indicate a nuclear isomer, a metastable or energetically-excited nuclear state (as opposed to the lowest-energy ground state), for example $\ce{^{180\mathrm{m}}_73Ta}$ (tantalum-180m).