# Question #da31f

Sep 4, 2016

We can write is as $\text{ "^{46}"Ca}$ or $\text{ "_{20}^{46}"Ca}$.

#### Explanation:

In an atomic symbol for an isotope:

The mass number (total protons plus neutrons) goes to the upper left of the chemical symbol:

$\text{ "_{20}^{color(blue)(46)}"Ca}$

The atomic number (protons only) goes to the lower left of the chemical symbol:

$\text{ "_{color(blue)20}^{46}"Ca}$

We sometimes leave off the atomic number because the chemical element has a uniquely defined atomic number:

$\text{ "_{20}^{46}"Ca = " ^{46}"Ca}$.