When the alkali metals are cut, they initially appear shiny grey but quickly become dull and white as they react with oxygen in the air. This is known as tarnishing. Sodium tarnishes more quickly ...

Oxygen-28 is not the only isotope where 20 neutrons no longer seem to be magic. In a phenomenon known as the island of inversion, isotopes of neon, sodium, and magnesium with 20 neutrons also show ...