Ernest Rutherford
Overview
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
(30 August 1871 – 19 October 1937) was a New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
-born British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
chemist
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...
and physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
who became known as the father of nuclear physics
Nuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
. In early work he discovered the concept of radioactive half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
, proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation, proving that the former was essentially helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
ions.
Unanswered Questions
Quotations
Radioactivity is shown to be accompanied by chemical changes in which new types of matter are being continually produced. ... The conclusion is drawn that these chemical changes must be sub-atomic in character. 
"The Cause and Nature of Radioactivity" in Philosophical Magazine (September 1902)
All science is either physics or stamp collecting.
As quoted in Rutherford at Manchester (1962) by J. B. Birks
If you can't explain your physics to a barmaid it is probably not very good physics.
As quoted in Journal of Advertising Research (March-April 1998)
We've got no money, so we've got to think.
As quoted in Quips, Quotes, and Quanta by Anton Z. Capri, page 65.