# Chemistry

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When you look up the atomic masses of Si and Sn and then find the average and then look up the atomic mass of Ge, what is discovered? does it lend supporting evidence to the periodicity of elements?

• Chemistry -

Why not look up Si and Sn, take the average and compare with that of Ge? You don't need an outsider to do that for you.

• Chemistry -

yes but how is it compared

• Chemistry -

Well, let's see.
Si = 28.08
Sn = 118.71
So the average is (28.08 + 118.71)/2 = 73.4. Do you think that is anywhere near the atomic mass of Ge (at 72.6)? It looks to me that it is. Try that for some other "triads." For example, look at the Li, Na, K triad.
Li = 6.9
K = 39.1
Average is (6.9 + 39.1)/2 = 23
How do you think that compares with 22.99 for Na? Do you think it is close?
The whole idea here is that in a group of 3 elements that the middle element in the column is very close to the average of the atomic masses of the first and last.

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