Thread: Gold VS Lead

Lead has a greater atomic mass than gold (196.97 VS 207.2) but yet, Gold is nearly twice as heavy as lead (19320 kg/cu.m VS 11340 kg/cu.m).

How can that be?

I would hazard a guess that gold atoms have a much smaller atomic radius than lead atoms.

i'm not sure but as i remember my periodicity you get small atomic radius as you got a long a period. So lead will be smaller and gold.

However to answer the question i would have to to say that it has to be the crystal structure of lead means that it is less dense than gold.

I must insist on the use of the term density rather than weight, as density specifically describes mass in a volume. Ice and water for example, both have THE SAME chemical formula, ice however has a much lesser density than liquid water. This is because of the effects that the crystaline structure that ice imparts. I suggest therefore that Gregchf is heading the right direction at least. The fact that the same physical volume of lead ways less than the equivalent volume of gold must suggest that the atoms are packed considerably more tightly together. I would not be comfortable in suggesting an actual structure of the unit cell for either metal, but i dare say that there is someone would be.

Originally Posted by Gregchf

i'm not sure but as i remember my periodicity you get small atomic radius as you got a long a period. So lead will be smaller and gold.

This applies to periods 1-3, but probably not to the d-subshell.

Alternatively, the s&d subshells can both delocalise in gold, and so hold the atoms closer together, with a stronger force.

The outer electrons (valence electrons) on gold are a lot closer to the nucleus than the outer electrons of lead. This is mostly because d electrons are very bad at shielding other d electrons from the nucleus's positive charge, so the d valence electrons on gold experience a lot more attractive positive charge, and are therefor pulled closer to the nucleus, than the s valence electrons on lead.