Calculating Average Atomic Mass, Slides of Chemistry

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Calculating Average Atomic Mass

So, why do the elements on

the PT have masses with

decimals???

Isotopes are atoms from

the same element

(therefore containing the same number of protons)

which have different

numbers of neutrons.

To calculate the

average atomic mass:

1. Multiply the mass of each

isotope by the % of theisotope

2. Add the products

76% of chlorine has a mass of 35

amu. The other 24% has a mass

of 37 amu. Calculate the average

atomic mass of chlorine.

35.48 amu

Sulfur has three main isotopes.

95% is Sulfur-32, 4% is Sulfur-34,

and 1% is Sulfur-

33. Calculate the

average atomic mass of sulfur.

32.09 amu