Origins of Chemistry — Founding Scientists & Theories

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by CrashCourse

This video will introduce you to chemistry during the Enlightenment in the 1700s. During this time in France, there was a huge movement supporting rational thought and the pursuit of knowledge. This was also when the first encyclopedia was created. This massive collection of books, however, focused a lot on qualitative measurements (describing how something looks or acts). Enlightenment thinkers wanted to shift away from that to quantitative data (describing with numbers), so they started to create standard measurements. Many new instruments, like the barometer, and even statistics were created at this time as well.

Around the same time, philosophers were experimenting with an invisible ether, or substance, called "phlogiston". This ether was supposedly released from combustion. Phlogiston Theory worked qualitatively, but it was hard to quantify with numerical data.

The person who eventually turned chemistry into a quantitative science was Antoine Lavoisier, who also worked on the metric system. Through his work, he concluded that the mass of matter stays the same, even if it changes shape or form. He also created and named a list of modern elements. He published his findings in what became the first modern chemistry textbook. This new textbook pushed out phlogiston theory and became the new, central way of thinking in chemistry.

Important Chemists Throughout History

Here are just some of the founding scientists and theories that shaped the field of chemistry:

Francis Bacon

Francis Bacon was a 17th century English philosopher.

Major contributions:

• Developed the scientific method
• Laid down the foundation for the scientific revolution

Robert Boyle

Robert Boyle was a 17th century chemist and often considered one of the founders of modern chemistry.

Major contributions:

• Developed Boyle's Law which described the behavior of gases
• Advocated for the use of the scientific method

John Dalton

John Dalton was an English chemist and physicist in the 1700's and 1800's.

Major contributions:

• Developed the atomic theory
• Discovered Dalton's law of partial pressures
• Discovered the law of multiple proportions

Antoine Lavoisier

Antoine Lavoisier was an 18th century chemist.

Major contributions:

• Discovered the law of conservation of mass
• Discovered and named the elements hydrogen and oxygen
• Discovered the role of oxygen in combustion reactions
• Helped construct the metric system
• Helped create a system for naming compounds (nomenclature)

Marie Curie

Marie Curie was a Polish and French chemist and physicist in the late 19th century and early 20th century. She was the first woman to win a Nobel Prize and the only person to win the prize in two different fields, chemistry and physics.

Major contributions:

• Discovered polonium and radium
• Carried out extensive research on radioactivity and its applications

The history of chemistry is a journey from ancient civilizations to our modern day. We know that ancient societies used chemistry concepts without even knowing it! However, chemistry became a scientific discipline in 430 BC. In 430 BC, Democritus defined the atom as the smallest unit of matter. Democritus' definition launched a winding history. We will start with the earliest forms of pseudo-science. By the end, we will reach the start of quantum mechanics.

Ancient Times to the 1500s:

The first person to expand on Democritus' definition was Aristotle in the 300s BC. Aristotle proposed that matter is composed of four elements: fire, air, water, and earth. Aristotles' proposal was the basis of alchemy. Alchemy was the belief that by combining the different elements in the correct way, the alchemist could make new materials. The main goal was to convert cheap metals into valuable gold. It was basically a get-rich-quick scheme.

The 1600s:

It wasn't until the 1600s that alchemy would begin to transform into what we call chemistry. In the early 1600s, Francis Bacon proposed that we could learn about the world through observation. Bacon laid the groundwork for our modern scientific method. In the late 1600s, Robert Boyle expanded on Bacon's ideas by emphasizing experimentation. Boyle's emphasis on experimentation led him to disagree with Aristotle's four elements. Bacon's and Boyle's ideas laid the foundation for the 1700s and the start of modern chemistry.

The 1700s:

In the 1700s, Antoine Lavoisier and Joseph Priestley would conduct some of the most important experiments in chemistry! Lavoisier experimented with combustion reactions, an important chemical reaction we use everyday. He showed that when phosphorus (P) was combusted, it gained mass. We know today that the combustion reaction leads to phosphorus reacting with oxygen. At the same time, Joseph Priestley was heating mercuric oxide and producing oxygen gas. Today we call this a decomposition reaction. Although they did not know it at the time, they had proved the existence of elements and compounds!

Toward the end of the 1700's, Joseph Proust published the Law of Definite Proportions, also known as the Law of Constant Composition which states that the ratio of elemental components are fixed in a compound. This law laid an important foundation for stoichiometry.

The 1800s:

The 1800s had a series of important developments. The first was in 1803 when John Dalton proposed his atomic theory. Dalton's atomic theory explained the physical and chemical properties of matter. Next, was the creation of the periodic table by Dmitri Mendeleev in 1869. Folklore tells us that Mendeleev had a dream where the elements arranged themselves into a table. More realistically, Mendeleev noticed that if he arranged the elements by atomic mass he was able to predict some of their properties. He even predicted some of the properties of undiscovered elements. For example, Mendeleev predicted the properties of Gallium (discovered in 1875)! Finally, in the 1890s, Pierre and Marie Curie discovered radioactivity. Their work in radioactivity would be the foundation for some of the most important discoveries of the 1900s. Sadly, Marie Curie died of long-term radiation exposure.

The 1900s:

In 1906, Ernest Rutherford conducted one of the most important experiments in modern chemistry, the Gold Foil Experiment. Rutherford launched alpha particles (basically a Helium nucleus) at a sheet of gold foil and measured the deflection angles. The deflection of the alpha particles demonstrated that the nucleus of an atom was positively charged. Rutherford also concluded that electrons orbited around the positively charged nucleus and that the nucleus must contain neutrons. His conclusions led him to develop the nuclear model of the atom.

Rutherford's experiments paved the way for two other important ideas. In 1916, Neils Bohr concluded that electrons existed in atomic orbitals that had specific energies. Bohr then proposed a new model of the atom, now called Bohr's atomic model. The second was Gilbert Lewis' Valence bond theory. Valence Bond theory proposed that covalent bonds form by the sharing of pairs of valence electrons.

Finally, in the 1920's we have Lewis De Broglie and Erwin Schrodinger who start modern quantum mechanics. De Broglie applied the wave-particle duality to Bohr's atomic orbital model. Shrodinger created a mathematical equation. We very creatively call his equation the Schrodinger Equation. The Schrodinger Equation mathematically describes an atom's orbitals.