Isotopes and relative atomic mass

How do you work out the relative atomic mass of an element from its isotopic abundance.

-Multiply each relative isotopic mass by its isotopic abundance and add up the results. - Divide by the sum of the abundance (if the abundance is given as a percentage it will be 100.)

Different isotopes of an element occur in different quantities, or isotopic abundance.

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Explain how the relative atomic mass of chlorine is found?

Chlorine has two stable isotopes, chlorine 35 and chlorine 37. There is a quite a lot of chlorine 35 and not so much chlorine 37- so chlorine's Ar works out as 35.5

What happens if an element has more than one isotope?

If an element has more than one isotope, its Ar (relative atomic mass) will be the average of the mass numbers of all the different isotopes , taking into account how much there is each one. So it may not be a whole number.

What happens if an element has only one isotope?

If an element only has one isotope, its Ar (relative atomic mass) will be the same as its mass number.

What are isotopes?

Isotopes are different forms of the same element, which have the same number of protons but a different number of neutrons.

So what do isotopes have?

So isotopes have the same atomic number but different mass numbers.

In the periodic table, the elements all have two numbers next to them, which is the bigger one?

The bigger one is the relative atomic mass (Ar) of the element.

What is the relative atomic mass?

The relative atomic mass of an element is the average mass of one atom of the element, compared to 1/12 of the mass of one atom of carbon 12.