Amedeo Avogadro is best-known for having discovered the law and accompanying number that are named in his honor. Avogadro's constant and Avogadro's number were critical breakthroughs in the development of modern chemistr... More »

Avogadro's number, also called Avogadro's law, creates a constant value for different gases, regardless of weight and structure, which makes it a foundational law in chemistry. Italian scientist Amedeo Avogadro created h... More »

Periodic law, also known as Mendeleev's law, is the concept that the chemical and physical properties of elements are based on an element's atomic weight when arranged by increasing periodic atomic number. Periodic law w... More »

John Dalton discovered that elements are only able to combine atomically when they are in fixed ratios. This discovery led to the basis for Dalton's Atomic Theory. More »

Because ancient Greek thinkers such as Democritus lacked sophisticated technology and tools such as the microscope, his theory of the atom was due more to thought experimentation than to hard empirical observation, as us... More »

English chemist Joseph Priestley discovered oxygen by reacting mercury oxide with heat through the use of a burning lens. Although the element was isolated by Swedish pharmacist Carl Wilhelm Scheele prior to Priestley's ... More »

Ernest Rutherford's famed Gold Foil Experiment of 1909 demonstrated that atoms were made up of a charged nucleus orbited by electrons. He published his findings in 1911 with a description of what he called the Rutherford... More »