液氧
The ground state of has a bond length of 121 pm and a bond energy of 498 kJ/mol. It is a colourless gas with a boiling point of . It can be condensed from air by cooling with liquid nitrogen, which has a boiling point of . Liquid oxygen is pale blue in colour, and is quite markedly paramagnetic due to the unpaired electrons; liquid oxygen contained in a flask suspended by a string is attracted to a magnet.