# Chemistry

The radius of a magnesium atom is 160 pm & its mass is 4.04 X 10^-23 g. What is the density of the atom in grams per cubic centimeter?

Assume the atom is a sphere with:
Volume= (4/3)*pi*r^3

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1. well I think it is 173 pm but oh well
r = 160 * 10^-12 m * 10^2 cm/m
= 160 *10^-10 cm = 1.6 *10^-9 cm

vol = (4/3)pi (1.6)^3 * 10^-27 cm^3
= 17.2*10^-27 cm^3

so
4.04*10^-23/(17.2 * 10^-27)
= .235 * 10^4 g/cm^3
= 2350 g/cm^3

check my arithmetic !

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2. well I think it is 173 pm but oh well
r = 160 * 10^-12 m * 10^2 cm/m
= 160 *10^-10 cm = 1.6 *10^-8 cm

vol = (4/3)pi (1.6)^3 * 10^-24 cm^3
= 17.2*10^-24 cm^3

so
4.04*10^-23/(17.2 * 10^-24)
= .235 * 10^1 g/cm^3
= 2.350 g/cm^3

more reasonable

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3. I did a double take for 2350. Hg, Au, U etc not even close to that.

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4. I had a hunch it might not be quite that heavy :)

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