August 28th, 2020 
The HW is different from what was posted on the original course schedule. Please do the following–
(1) List the 5 most abundant chemical elements (not compounds) (a) in the Earth’s crust, and (b) in the human body. (No calculation required; just cite your source.)
(2) (a) Estimate the number of atoms in an ordinary sheet of paper. (b) If all these atoms were lined up in a straight line, like a chain with each atom one “link”, would that “chain” reach from the Earth to the Moon, or even further, or not as far? Show rough calculations in support of each answer.
(3) Look up “xkcd radiation chart” (on the internet or from the lecture slide). Write down FOUR facts from it which you think are important – and perhaps surprising – to know.
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