# What is the isotopic symbol for 18 protons and 23 neutrons?

This is the ""^41Ar isotope.
This is not a common argon isotope. The fact that there are 18 protons, i.e. 18 positively charged, massive nuclear particles, immediately specifies the argon element, and thus I don't have to write $Z$, $\text{the atomic number}$. There are $\text{23 neutrons}$ contained in this nuclide to give a mass of $41 \cdot \text{amu}$