Why Gold is more dense than lead?

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Discussion Overview

The discussion centers on the question of why gold is denser than lead despite lead having a higher atomic mass. Participants explore the relationship between atomic mass, atomic radius, and density, considering both theoretical and empirical aspects.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes the atomic numbers of gold (79) and lead (82) and their respective densities (19,000 kg/m³ for gold and 11,000 kg/m³ for lead).
  • Another participant references scatter plots of density and discusses the periodic peaks in density relative to atomic mass, suggesting a complex relationship.
  • A participant explains that the density of an element is related to both atomic mass and atomic density, highlighting that gold atoms are more tightly packed than lead atoms due to smaller atomic radii and bond lengths.
  • Another participant emphasizes the formula for density (density = mass/volume) and suggests that both mass and volume should be considered in understanding the density differences between gold and lead.

Areas of Agreement / Disagreement

Participants present multiple viewpoints regarding the factors influencing density, including atomic mass, atomic radius, and packing efficiency. The discussion remains unresolved with no consensus on a singular explanation.

Contextual Notes

Participants reference specific atomic radii and bond lengths, but the implications of these measurements on density are not fully resolved. The discussion relies on empirical data and theoretical relationships without definitive conclusions.

yasar1967
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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??
 
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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.

http://www.webelements.com/webelements/elements/text/Au/radii.html
The atomic radius for Au is ~ 135 pm, and the Au-Au bond length ~ 288.4 pm.

http://www.webelements.com/webelements/elements/text/Pb/radii.html
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.
 
thank you
 
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...)
 

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