# Question #9d7ae

Dec 21, 2017

See below

#### Explanation:

First of all, let's identify the element and write it in Isotope Notation.

Since the Atomic Number is equal to the number of protons, all we have to do is get our periodic table and find the element with an atomic number of 31.

This is Gallium.

Then, we write it in isotope notation as follows:

![https://d2jmvrsizmvf4x.cloudfront.net/amk2UvEQteqTemzr2fIY_Isotope_Notation.jpg)

But hang on, two more electrons were added! That means that there is an overall negative charge of $- 2$. Write it like this: $G {a}^{2 -}$ This is an Anaion

To find the Mass Number, all we have to do is add the number of protons and neutrons. We get $31 + 39 = 70$.