Half-life, Theory of Radioactive Change, and Transmutation

Throughout his life, Rutherford made several important discoveries. The most notable are arguably his discovery of alpha and beta particles, and the development of the Rutherford model of the atom. However, he made several other important contributions including: half–life, the theory of radioactive change, and successfully carrying out transmutation.

Half-Life:

While he was in Montreal, Rutherford began working with thorium, another radioactive element. He discovered that the number of radioactive atoms in a sample of thorium decrease exponentially over time. ^[1] This led to the development of the concept of half-life. Half-life is the amount of time needed for half of the atomic nuclei of a radioactive sample to decay. ^[2] Each radioactive element has its own unique half-life.

Theory of Radioactive Change:

In 1902, Rutherford and Frederick Soddy proposed an explanation for radioactivity, in which the energy of radioactivity came from within the atom. Also, they proposed that the loss of an alpha or beta particle meant that the element had changed into a different element. ^[3] Rutherford and Soddy expected some resistance to their theory, as it bore a certain similarity to alchemy, however, the experimental evidence they gathered quickly quelled opposition. ^[4]

Transmutation:

In 1919, at the end of his stay at Manchester, Rutherford became the first person to intentionally transmute one element into another. By bombarding nitrogen atoms with alpha particles, he successfully made an isotope of oxygen, plus a positive particle, which he called a proton. ^[5]

[1] http://rsbm.royalsocietypublishing.org/content/obits/2/6/394
[2] http://www.britannica.com/EBchecked/topic/252386/half-life
[3] http://rsbm.royalsocietypublishing.org/content/obits/2/6/394
[4] http://www.britannica.com/EBchecked/topic/514229/Ernest-Rutherford-Baron-Rutherford-of-Nelson
[5] http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-bio.html