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From: gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>)
Newsgroups: net.physics
Subject: Re: electrons
Message-ID: <1994@brl-tgr.ARPA>
Date: Sat, 25-Jan-86 23:25:41 EST
Article-I.D.: brl-tgr.1994
Posted: Sat Jan 25 23:25:41 1986
Date-Received: Wed, 29-Jan-86 04:14:50 EST
References: <1165@homxb.UUCP>
Organization: Ballistic Research Lab
Lines: 28

> I am not really into physics so I can't figure this out
> I need to know how to calculate the number electrons in
> a solid copper sphere 10cm in diameter. 

This seems to be a strange "need" you have.  Assuming you
really want the total number of electrons and not just the
number of "free" (conduction) electrons:

Volume of sphere = 4/3 Pi r^3, where r = 5cm, => 523.6 cc

Density of copper at S.T.P. = 8.9 g/cc

Mass of sphere = density * volume => 4660 g

Atomic weight of copper = 63.54 g/mole

Moles in sphere = mass / at.wt. => 73.3 moles

Avogadro's number = 6.02 * 10^23 atoms/mole

# atoms in sphere = moles * Avogadro => 4.4 * 10^25 atoms

# electrons per atom = atomic number = 29

# electrons in sphere = # atoms * (electrons/atom) =>
	1.3 * 10^27 electrons

So tell us, what good is this information?