This article looks at the events that led to the discovery of isotopes in the early part of the 20th century. It is difficult to claim that the discovery was a single event. A number of famous scientists worked independently to provide the evidence, and the understanding of the need to think differently about atoms gradually emerged. Four varied…

This "Science note" examines the bromination of phenol, a reaction that is commonly taught at A-level and IB (International Baccalaureate) as an example of electrophilic substitution. Phenol undergoes bromination with bromine or bromine water at room temperature. A white precipitate of 2,4,6-tribromophenol is rapidly formed. This…