Why Gold Is Golden

Relativity inside heavy atoms

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Inner electrons of heavy atoms move at roughly $Z/137$ of light speed.
• Relativistic contraction changes chemistry: gold is yellow and mercury is liquid because of it.
• The simple estimate breaks down near $Z = 137$; the true limit of the table is unknown.

Steps

1. Electrons near light speed
2. How fast?
3. Gold’s factor
4. The colour of gold
5. Liquid mercury
6. The end of the table?