Question

Describe how to use the information from the mass spectrum to determine the average atomic mass of the element.

Answer 1

`A=\sum_i A_i r_i`

Step-by-step explanation:

Before answering the question, we introduce two definitions:

- Isotope: isotopes of the same element are atoms of the same element having same number of protons but different number of neutrons --> this means that they have same atomic number, but different atomic mass

- Relative abundance: each isotope is present with a certain relative abundance, which gives the % of that isotope compared to the total.

When we know the mass spectrum of a certan element, it means we know the relative abundance of each isotope, together with the atomic mass of the isotope.

For instance, we can have:

- Isotope 1 with atomic mass
`A_1` and relative abundance
`r_1`, where
`r_1` is a fraction in the form
`(r)/(100)` (it gives the percentage of that isotope relative to the total)

- Isotope 2 with atomic mass
`A_2` and relative abundance
`r_2`

... and so on

So, the average atomic mass of the element is calculated with the formula:

`A=\sum_i A_i r_i`

So, basically by calculating the sum of the product of each atomic mass by its relative abundance.