Robert S. Mulliken

Robert Mulliken was a smart scientist. He studied how tiny parts make up things. He found a new way to see how these parts stay together. This way is called a new theory.

He worked at a big school in Chicago. He also taught at a school in New York. He was very good at science. He won a very big prize for his work.

Robert had a father who was a teacher too. He learned many names of plants when he was small. He even learned a new way to talk. He was a great helper to his father. He worked hard to learn more every day.

Robert Mulliken was a famous chemist. He was born in 1896. His father was a teacher of chemistry too. As a boy, Robert had a great memory. He learned many names of plants. He even learned the German language.

Robert went to a school called MIT. He studied chemistry there. Later, he went to the University of Chicago. He worked with many great scientists. Some of them won big prizes too. In 1927, he worked with a man named Friedrich Hund. Together, they made a new idea. This idea is called molecular orbital theory.

This theory is a way to study molecules. Molecules are tiny parts of our world. Before this, scientists used a different way. That way was called valence-bond theory. But Mulliken's way was more flexible. It helped scientists study many kinds of molecules. Because of this work, he won the Nobel Prize in Chemistry in 1966. He also won the Priestley Medal in 1983. Robert Mulliken lived to be 90 years old. He died in 1986.

Robert Sanderson Mulliken was a very important American physical chemist. He was born on June 7, 1896, in Newburyport, Massachusetts. His father, Samuel Parsons Mulliken, was a professor at MIT. As a young boy, Robert had a very good memory. He could remember the names of many different plants. He even learned the German language well enough to skip classes in college.

Mulliken's work changed how we understand molecules. Molecules are tiny building blocks that make up everything. He helped develop molecular orbital theory. This is a way to calculate how molecules are built. Before this, many scientists used the valence-bond method. That older method looked at bonds as being between pairs of atoms. Mulliken's theory was different and more flexible. It describes electrons as being in states that spread over an entire molecule. This helped scientists study many different types of molecules and fragments.

Mulliken's path to discovery involved many famous places. He graduated from MIT in 1917. During World War I, he worked in Washington, D.C. Later, he earned his Ph.D. from the University of Chicago in 1921. He also studied at Harvard University. In 1925 and 1927, he traveled to Europe. There, he met many great scientists like Erwin Schrödinger and Werner Heisenberg. These men were all working on new ideas in physics.

In 1927, Mulliken worked with a scientist named Friedrich Hund. Together, they created the Hund-Mulliken theory. This work was very special because it sat between chemistry and physics. He taught at New York University and the University of Chicago. In 1936, he became a member of the National Academy of Sciences. He was the youngest person to join that group at that time. He later became a professor at Florida State University in 1961.

Many people recognize Mulliken because of his big awards. He won the Nobel Prize in Chemistry in 1966. He also received the Priestley Medal in 1983. Scientists even use a method called Mulliken population analysis to study atoms. This method helps assign charges to atoms in a molecule. His life shows how studying tiny things can explain the whole world. He lived to be 90 years old. He passed away on October 31, 1986, in Virginia.

Robert Sanderson Mulliken was a highly influential American physical chemist. He is most famous for his role in developing molecular orbital theory. This theory provides a mathematical method for computing the structure of molecules. Molecules are the tiny particles that make up all matter. By understanding how electrons behave within these structures, scientists can better predict how substances interact. Mulliken's work helped bridge the gap between the fields of chemistry and physics. His contributions changed how researchers view the electronic landscape of a molecule.

To understand his work, one must look at the mechanism of molecular orbital theory. Before Mulliken, many scientists used the Valence-Bond (VB) method. This method, also called the Heitler-London-Slater-Pauling method, focused on localized bonds. It described bonds as overlapping atomic orbitals centered on specific pairs of atoms. While useful, the VB method struggled to calculate the properties of excited states. An excited state occurs when a molecule absorbs an energy source. Mulliken’s approach was different and more flexible. He described electron wave functions as delocalized molecular orbitals. In this model, electrons are assigned to states that extend over an entire molecule rather than staying between two atoms. This allowed for a much wider application to various molecule types.

There are distinct ways to look at chemical bonding in science. The first is the Valence-Bond method, which was very popular because it matched chemists' traditional ideas. The second is the molecular-orbital method, often called the Hund-Mulliken theory. This version was developed through the collaboration of Mulliken and Friedrich Hund. This theory proved more capable of describing the symmetry of a molecule. It also worked well for complex molecular fragments. Because of this flexibility, the molecular-orbital method eventually eclipsed the older Valence-Bond method in many scientific uses.

Mulliken's journey began in Newburyport, Massachusetts, on June 7, 1896. His father, Samuel Parsons Mulliken, was a professor of organic chemistry at MIT. Robert showed an excellent, though selective, memory as a child. He learned the botanical classification of plants and became fluent in German. He graduated from MIT in 1917 with a B.S. in chemistry. During World War I, he worked in Washington, D.C., producing poison gas. This period was difficult, as he suffered burns and later contracted influenza. He eventually earned his Ph.D. from the University of Chicago in 1921. His early research focused on the separation of mercury isotopes by evaporation.

His scientific growth accelerated through travel and high-level collaboration. In 1925 and 1927, Mulliken traveled to Europe to work with legendary scientists. He met figures like Erwin Schrödinger, Werner Heisenberg, and Max Born. These men were developing the new quantum mechanics that would replace old quantum theory.

He was particularly influenced by Friedrich Hund. In 1927, their work together resulted in the Hund-Mulliken theory. This period established Mulliken as a scientist who worked on the borderline of physics and chemistry. He later held positions at New York University and the University of Chicago.

Mulliken's achievements earned him many prestigious honors and significant numbers. In 1936, he became the youngest member of the National Academy of Sciences in its history. He received the Nobel Prize in Chemistry in 1966. He also earned the Priestley Medal in 1983. In 1934, he created a new scale for measuring electronegativity. This is the tendency of an atom to attract electrons. His scale was based on the average of an atom's ionization enthalpy and electron affinity. He also directed the Information Office for the University of Chicago's Plutonium project from 1942 to 1945.

Beyond his main theory, Mulliken left several lasting legacies in science. One is the Mulliken population analysis. This is a specific method used to assign electrical charges to atoms within a molecule. He also spent time at Florida State University as a Distinguished Professor starting in 1961. His studies ranged from simple diatomic molecules to very large, complex aggregates. He even helped found the World Cultural Council in 1981. These diverse interests show how his understanding of molecular structure connected to many different scientific systems.

Robert Mulliken lived a long and productive life. He married Mary Helen von Noé in 1929, and they had two daughters. He continued his research into acid-base reaction theories using quantum mechanics in 1952. He eventually retired in 1985. Mulliken passed away at the age of 90 on October 31, 1986. He died of congestive heart failure at his daughter's home in Arlington County, Virginia. His body was returned to Chicago for burial, marking the end of a career that fundamentally reshaped modern chemistry.