The atomic nucleus is a complicated place that operates much like the electrons that surround it, as a shell model. That is, as more protons or neutrons are added, and the atomic number goes up, there are certain numbers where the energy that binds the nucleus together is significantly higher than it is for other numbers.
These are called magic numbers, and at them, the protons and neutrons are arranged into complete shells, making the nucleus much more stable than that of other nuclei. As of this writing, there are seven recognized magic numbers: 2, 8, 20, 28, 50, 82, and 126 which is only for neutrons.
These numbers correspond to the elements helium, oxygen, calcium, nickel, tin, lead, and the hypothetical element unbihexium. In 1949, three physicists discovered the nuclear shell model, and in 1963, they received the Nobel Prize in Physics for their work. You might be surprised to know that one of the three was a woman.
Two remarkable women from Poland
Like her fellow compatriot Marie Curie, who was the first woman to win a Nobel Prize in Physics, Maria Goeppert was born in Poland, which at the time was part of Prussia. Soon after her birth, her family moved to Göttingen, where her father became a professor at the city's famous University of Göttingen.
In 1924, Goeppert entered the University of Göttingen to study mathematics. The university already had a famous woman there teaching mathematics — Emmy Noether. Segueing into physics, Goeppert pursued a Ph.D., then went on to collaborate with one of the fathers of quantum dynamics, Max Born.
In 1930, Goeppert married American chemist Joseph Edward Mayer, who was working at the University of Göttingen, and the two moved back to the U.S. Mayer took a job as a professor of chemistry at Johns Hopkins University, but when Maria applied for a job there, she was turned down, with the university citing its rules on nepotism.
Instead of a professorship, the school offered Goeppert-Mayer a job translating German correspondence, but being on campus allowed her to continue her work in physics. In 1935, she published an influential paper on double beta decay.
In 1937, Joseph Mayer was fired from his job at Johns Hopkins because of his wife's presence in his laboratory. Maria then took an unpaid job at New York's Columbia University, which brought her into contact with the physicists Harold C. Urey and Enrico Fermi, who had both fled Nazi Germany in 1939. It was Fermi who in 1942 created the world's first nuclear reactor.
Fermi tasked Goeppert-Mayer with examining the valence shells of as yet undiscovered transuranic elements. These are the chemical elements that lie beyond uranium in the periodic table and have atomic numbers greater than 92. Goeppert-Mayer correctly predicted that the form these elements would take would be similar to that of the rare earth elements.
Partnering with "Dr. Strangelove"
By 1942, Goeppert-Mayer had joined the Manhattan Project, which was America's attempt to build an atom bomb. At Los Alamos, New Mexico and later at the University of Chicago, she worked with Dr. Edward Teller who is considered the father of the hydrogen bomb. Teller is also said to be the inspiration for the character of Dr. Strangelove, played by Peter Sellers in Stanley Kubrick's 1964 movie of the same name.
Following the war, both Joe and Maria Mayer joined the faculty at the University of Chicago, where she developed a mathematical model for the nuclear shells. She likened it to dancers waltzing within a room:
" ... all the dancers are spinning twirling round and round like tops as they circle the room, each pair both twirling and circling. But only some of those that go counterclockwise are twirling counterclockwise. The others are twirling clockwise while circling counterclockwise. The same is true of those that are dancing around clockwise: some twirl clockwise, others twirl counterclockwise."
One of only three
In 1960, Goeppert-Mayer moved to the University of California, San Diego, and in 1963 when she received the Nobel Prize in Physics along with German physicist Hans D. Jensen and American physicist Eugene Wigner, she became only the second female recipient of that prize. No woman was awarded that prize until 2018 when Canadian optical physicist Donna Strickland became the third woman to receive the Nobel Prize in Physics for her work with pulsed lasers.
A series of honors
Following Goeppert-Mayer's death in 1972, the American Physical Society (APS) created the Maria Goeppert-Mayer Award, which is awarded to female physicists. A crater on the planet Venus, Crater Goeppert-Mayer is named after her.
In 2011, Goeppert-Mayer was included in the third issue of the American Scientists collection of postage stamps, along with biochemist Melvin Calvin, botanist Asa Gray, and physician/biochemist Severo Ochoa. You can see that stamp at the top of this article.
At the University of California, San Diego, the physics department is housed in Mayer Hall, which is named after Maria Goeppert-Mayer and her husband Joe, ensuring that future generations will remember a woman who quite literally changed the world.