Gallium melts at 29.76 °C and is widely used in semiconductor circuits (Gallium Arsenide).
Core Principles & Analysis
Paul-Emile Lecoq de Boisbaudran discovered gallium spectroscopically in 1875, and its properties matched Mendeleev's predicted 'eka-aluminium' almost exactly, vindicating the periodic table.
Melting at 29.8 C, it liquefies in the palm of a hand, yet does not boil until about 2,400 C, one of the widest liquid ranges of any element.
Gallium arsenide and gallium nitride semiconductors enable smartphone chips, laser diodes, and the blue LEDs that won the 2014 Nobel Prize and made white LED lighting possible.