Using a mixture of ultracold sodium (Na) and potassium (K) atoms, Shi's team weakly associated these single particles into diatomic NaK molecules. This is where the technical difficulties really ...

Bromine is one of only two liquid elements. Iodine is solid. They exist as diatomic molecules - they have two atoms in each molecule. As you go down the group the halogens become less reactive.

Bromine is one of only two liquid elements. Iodine is solid. They exist as diatomic molecules - they have two atoms in each molecule. As you go down the group the halogens become less reactive.