Relative Atomic Mass

Question 1

Relative atomic mass;
What is it?
Relative abundance?

Answer 1

It’s the average mass
Of all isotopes of an element.
It has to allow for the relative mass of each isotope and its RELATIVE ABUNDANCE

Question 2

What does it mean?

Answer 2

It is a way of saying how heavy different atoms are compared with the mass of an atom of carbon -12.
So carbon -12 has an A of exactly 12!

Question 3

What does relative abundance mean?

Answer 3

It means how much there is of each isotope compared to the total amount of the element in the world.

Tip: this can be shown in a ratio, percentage or a fraction

Question 4

Here’s an example: work out the relative atomic mass of chlorine:

Element Relative mass of isotope Relative abundance
35 3
Chlorine 37 1

Answer 4

Step 1) multiply the mass of each isotope by its relative abundance
Step 2) add those together
Step 3) divide by the sum of the relative abundances
A. = (35 x 3) + (37 x 1)
r. divided by
3 + 1