General Question

smile1's avatar

If the atomic number of an element increases, then density will increase as well because...?

Asked by smile1 (493points) October 8th, 2009

So for my class, i have to create a hypothesis for a lab about density and atomic numbers. I was thinking, that If the atomic number of an element increases, then density will increase as well because more protons are packed in a nucleus.

but…im not 100% sure…

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8 Answers

grumpyfish's avatar

Not necessarily—(although generally so)—Lead (82) is less dense than Osmium (76) at STP.

Mostly because, “it’s complicated” =)

smile1's avatar

I mean…generally.

ragingloli's avatar

chemistry classes are long gone, but i think it largely depends on the atomic mass and the number of electrons in the outer shell which will repel electrons of adjacent atoms.
but that is just my guess.

Les's avatar

Here is a table of the elements sorted by their densities. I’m going to agree with grumpyfish. The reason is because, it is complicated.

grumpyfish's avatar

@Les: great link!

Part of it is this: which affects certain elements density, mainly having to due with (if I’ve understood correctly) that the 4f electron level has some “funny properties”

smile1's avatar

well..i understand that…its just at a high school level, so mostly generic, adn we’re only talking about the p sublevels.

grumpyfish's avatar

@smile1 indeed—the important thing to remember (or learn?) is that it’s very hard to make generalizations about chemistry.

E.g., take the “things in a column are generally alike” Nitrogen & Phosphorus are similar to Arsenic chemically, but Nitrogen won’t kill you (directly).

virtualist's avatar

@smile1 The electron density IS a direct function of Z and A , utilizing Avogadros constant as well. It is an important parameter in medical imaging… e.g. CT scanners produce an image which is approximately a image of electron density spatial distributions in the body…. and they look very different in ‘diseased’ or ‘broken’ anatomic sites….......

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