Outermost shell of electrons in an atom. It contains the valence electrons. Elements with four or more electrons in their outermost shell can show variable valence. Chlorine can show valences of 1, 3, 5, and 7 in different compounds.
Although often coloured yellow, the island is intended to be copper, reflecting the country's name, ‘Copper Island’. Effective date: c. September 1960.