January 31 is Theodore William Richards’ birthday. Richards was an American chemist who gave the first chemical evidence of the existence of isotopes.
An element is determined by the number of protons in its nucleus. Isotopes of elements are determined by the number of neutrons with the protons in the nucleus. If an element has multiple isotopes, the element will have multiple atomic mass values. The atomic masses written on the periodic table are weighted averages of all the different isotopes of each element.
Richards spent an entire career systematically obtaining pure samples of elements and carefully determining each element’s atomic weight. From 1889 to 1932, he had obtained atomic weights for 55 different elements. His technique was so precise that he noticed an element’s atomic weight could vary by small amounts from sample to sample. He could not explain why different samples would have different masses. He would not have an explanation until 1913 when J.J. Thomson first identified two different isotopes of neon.
Richards would receive the 1914 Nobel Prize in Chemistry for his work and contributions to atomic structures. His work would be quickly surpassed by British chemist Francis Aston, who invented the mass spectrometer. This device would quickly and easily perform many of the same tasks Richards painstakingly spent his life trying to accomplish.
Notable Science History Events for January 31
1971 – Apollo 14 mission to Moon launched.
NASA launched the Apollo 14 mission to the Moon. It would become their third successful mission to the Moon. The mission also was the return of America’s first man in space, Alan Shepard as the commander of the mission. Astronauts Stuart Roosa and Edgar Mitchell completed the crew of Apollo 14.
Fun fact: Alan Shepard took two golf balls to the Moon. His club of choice was a six-iron head attached to a sample scoop handle. After one-handed strokes, he claimed the drive went “miles and miles and miles”.
1958 – The United States successfully launches their first satellite.
The United States launched their first satellite, Explorer 1, into orbit. This satellite discovered Earth’s Van Allen radiation belts. The Van Allen belts are a distribution of high energy ions held in place by Earth’s magnetic field.
1950 – The U.S. announces their hydrogen bomb project.
President Truman announced the program to develop the hydrogen (or fusion) bomb. The project produced bombs that use the energy produced by an atomic weapon to cause fusion of hydrogen in a second part of the bomb. This would release additional energy and make a much larger explosion. In just under three years, the United States tested their first thermonuclear device during Operation Ivy – Test Mike.
1929 – Rudolf Mössbauer was born.
Mössbauer is a German physicist who was awarded half the 1961 Nobel Prize in Physics for his research on the interactions between gamma rays and matter and the discovery of the Mössbauer effect. the Mössbauer effect describes the recoil-free absorption and transmission of gamma rays by atoms in solids.
1881 – Irving Langmuir was born.
Langmuir was an American chemist who was awarded the 1932 Nobel Prize in Chemistry with Dr. Katherine B. Blodgett. He was the first non-academic chemist to be awarded the prize. The work was primarily about monolayers and surface absorption and created an entirely new discipline of thin film chemistry. He also contributed to atomic theory by proposing that atoms try to complete their outer shells with eight electrons (the octet rule).