Why can gold be drawn out finer than light? The metal gold is extremely malleable. Gold is also ductile and one ounce can be drawn into 80 km (50 miles) of thin gold wire (5 microns diameter) to make electrical contacts and bonding wire.
I have heard this line Gold can be drawn out finer than light, as an advertising slogan, many times. 

Even if it is  a slightly loose definition of light, if you assume most non-physicists may consider light as visible light, ranging from  from 0.4 microns (blue) to 0.7 microns (red) then, as advertising slogans generally go, it's almost the truth. 
Even if we don't quibble about an order of magnitude here or there, it's still an impressive property.
How does the  molecular arrangement / crystal structure, of gold allow this level of ductility when drawn out, compared with elements such as copper or platinum? 
 A: A study undertaken by Nutting and Nuttall at the University of Leeds found that "gold is not inherently more ductile than other face-centered cubic metals", such as copper.  The authors found by experimentation that "gold is considerably less ductile in tension than silver." But when beaten foil becomes very thin, other metals tend to fragment, whereas gold holds together.
Under deformation, there is grain boundary sliding in metals.  If the foil gets to be thinner than the grain size, "new sub-grains can be formed by dislocation movements and interactions totally within the volume of the foil."  So not only do grain boundaries slide, but new grain boundaries can be formed.  It's likely that these sliding and multiplying grain boundaries are a significant contribution to the strain that flattens the foil under stress.
The only significant difference the authors could find to explain why gold does not fragment when beaten thin is that it's a noble metal with no film of surface oxidation.  Because the surface of the foil is free to deform, the energy of grain boundary dislocations is able to escape from the foil.  This "accommodates the imposed strain without preferential deformation occurring at the sub-grain boundaries."
