# Why Gold is more dense than lead?

1. Jan 28, 2008

### yasar1967

Gold has atomic number of 79 whereas Lead has 82 but lead has 11.000kg/m3 density as to Gold's 19.000kg/m3.

How come??

2. Jan 28, 2008

### Staff: Mentor

Look at the scatter plots of density here.
http://www.webelements.com/webelements/elements/text/Au/phys.html
http://www.webelements.com/webelements/elements/text/Pb/phys.html

Note the periodic peaks in density, even as atomic mass is gradually increasing.

Density of an element is related to Atomic Mass and Atomic Density. Atomic mass of Au is ~197 and that of Pb ~ 207. However, when we look at the atomic radii and bond lengths, those distances are smaller for Au than Pb.

The atomic radius for Au is ~ 135 pm, and the Au-Au bond length ~ 288.4 pm.

The atomic radius for Pb is ~ 180 pm, and the Pb-Pb bond length ~ 350.0 pm.

So the Au atoms are more tightly packed than Pb atoms, and thus even though the atomic mass of Pb (207) is greater than Au (197), the density of Au is greater than that of Pb.

3. Jan 28, 2008

thank you

4. Mar 1, 2008

### mysqlpress

density=mass/volume.
although gold has a lower atomic mass than Pb, the volume should also be considered.
that is the strucuture(size of Au/Pb and metallic bond radius...)