Emeléus was born in Poplar, London on 22 June 1903, the son of Karl Henry Emeléus (1869–1948), a pharmacist who was born in Vaasa, Finland. The family moved to the Old Pharmacy in Battle, Sussex shortly after Emeléus was born. His elder brother Karl George Emeléus (1901–1989), went on to become professor of physics at the Queen's University of Belfast.
Emeléus was educated at St Leonards Collegiate School, Hastings, and Hastings grammar school followed by the Royal College of Science, Imperial College, London, graduating in 1923. He gained his PhD in 1926 and a DSc three years later. During his post-graduate studies he spent time at the University of Karlsruhe as a student of Alfred Stock and two years at Princeton University with Professor Hugh Stott Taylor. Among his many students, notable is Norman Greenwood.
Emeléus served as president of the inorganic chemistry division of the International Union of Pure and Applied Chemistry (1955–60). He was also president of the Chemical Society (1958–60) and of the Royal Institute of Chemistry (1963–5).
- Edward Harrison Memorial Prize (1932)
- Tilden Lecture to the Chemical Society (1942)
- Fellow of the Royal Society (1946)
- Liversidge Award (1954)
- Alfred Stock Memorial Prize and medal of the Gesellschaft Deutscher Chemiker (1954)
- Commander of the Order of the British Empire (1958)
- Davy Medal of the Royal Society (1962)
- Henri Moissan prize for fluorine chemistry, Germany (1991)
- Lavoisier Medal of the Société Chimique de France (French Chemical Society)