Rutherfordium is a chemical element with symbol Rf and atomic number 104, named in honor of physicist Ernest Rutherford. It is a synthetic element (an element that can be created in a laboratory but is not found in nature) and radioactive; the most stable known isotope, 267Rf, has a half-life of approximately 1.3 hours.
In the periodic table of the elements, it is a d-block element and the second of the fourth-row transition elements. It is a member of the 7th period and belongs to the group 4 elements. Chemistry experiments have confirmed that rutherfordium behaves as the heavier homologue to hafnium in group 4. The chemical properties of rutherfordium are characterized only partly. They compare well with the chemistry of the other group 4 elements, even though some calculations had indicated that the element might show significantly different properties due to relativistic effects.
In the 1960s, small amounts of rutherfordium were produced in laboratories in the former Soviet Union and in California. The priority of the discovery and therefore the naming of the element was disputed between Soviet and American scientists, and it was not until 1997 that International Union of Pure and Applied Chemistry (IUPAC) established rutherfordium as the official name for the element.