All practice pages/Interatomic theory/Elements
Element 79, a transition metal
Beautiful, rare and almost indestructible, gold has been treasured for as long as people have made things.
Period 6, group 11. The other transition metals are tinted, and every cell opens its own article.
Gold has 79 electrons, one for every proton, so the atom carries no charge. Below are the same 79 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s¹
Short form: [Xe] 4f¹⁴ 5d¹⁰ 6s¹, where [Xe] stands for the 54 electrons xenon already has.
That list runs by shell. In the order the subshells fill it reads [Xe] 6s¹ 4f¹⁴ 5d¹⁰, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.
Gold sits in period 6 and has 6 shells. The period number counts the shells.
The outer shell holds 1 electron. Those are the ones gold can lose, gain or share, so they are the ones that decide what it bonds with.
Gold holds its electrons unusually tightly for a metal, so it resists oxygen, water and nearly all acids. Aqua regia, a mixture of nitric and hydrochloric acids, is one of the few things that dissolves it.
Found mostly as the metal itself, in quartz veins and as grains and nuggets in river gravels, and also in copper ores. China, Australia and Russia mine the most. All the gold ever mined would fit in a cube about 22 meters on a side.
Known since prehistory; gold objects from the Varna burial ground in Bulgaria are more than 6,000 years old. The name is Old English, and the symbol Au comes from its Latin name aurum.
Jewelry takes about half, and investment bars and coins much of the rest. Gold also plates electrical connectors that must never corrode, repairs teeth, and coats astronaut helmet visors and satellite parts to reflect heat. Gold nanoparticles make the colored line on many rapid tests.