Group 11: the coinage metals

A full d subshell plus one s electron

Copper is [Ar] 3d¹⁰ 4s¹, silver [Kr] 4d¹⁰ 5s¹ and gold [Xe] 4f¹⁴ 5d¹⁰ 6s¹. Like the alkali metals, each has one outer s electron, but the nucleus holds it far more tightly: copper’s first ionization energy is 7.726 eV, against 4.341 eV for potassium in the same period, and gold’s is 9.226 eV.

So these metals react far more slowly than group 1 metals. Silver forms Ag⁺, copper forms Cu⁺ and the more common Cu²⁺, and gold forms Au⁺ and Au³⁺, but only under harsh conditions.

Trends down the group

This group does not follow a smooth line. Melting points are 1357.77 K for copper, 1234.93 K for silver and 1337.33 K for gold. Density rises from 8.96 g/cm³ to 10.49 g/cm³, then nearly doubles to 19.3 g/cm³ for gold. Electronegativity is 1.9 for copper and 1.93 for silver, but 2.54 for gold, the highest of any metal.

Gold’s unusual numbers, and its yellow color, come from relativity. Near its heavy nucleus, gold’s electrons move at a large fraction of the speed of light, which shrinks the 6s orbital and changes the colors of light gold absorbs. Without that effect, gold would look silvery.

Where you meet group 11

Copper carries electricity in most household wiring and weathers to the green patina seen on old roofs and the Statue of Liberty. Silver is the best electrical conductor and the most reflective metal, used in mirrors, solar panels and electronics, though sulfur compounds in the air slowly tarnish it black. Gold coats electrical contacts that must never corrode, and all three are made into jewelry.

Roentgenium

Roentgenium (111), named after Wilhelm Röntgen, the discoverer of X-rays, has been made only a few atoms at a time, so its properties are predicted. Calculations suggest relativity changes it even more than gold, giving it the predicted configuration [Rn] 5f¹⁴ 6d⁹ 7s² instead of the d¹⁰ s¹ pattern above it.