Chemistry

Discovered that electrical charges come in 2 varieties – positive and
negative. Like charges repel, opposite charges attract.

Dalton’s Atomic Theory of Matter:
Matter is made up of atoms that are indivisible and indestructible. All atoms of an element are identical. (Known now to be untrue!) Atoms of different elements have different weights and different chemical properties. Atoms of different elements combine in simple whole numbers toform compounds.

Experiments with gases that first became possible at the turn of the nineteenth century led John Dalton in 1803 to propose a modern theory of the atom based on the following assumptions. ... Matter is made up of atoms that are indivisible and indestructible. John Dalton was the first to recognize that the total pressure of a mixture of gases is the sum of the contributions of the individual components of the mixture. By convention, the part of the total pressure of a mixture that results from one component is called the partial pressure of that component. Dalton's law of partial pressures states that the total pressure of a mixture of gases is the sum of the partial pressures of the various components.

Crookes discovered a previously unknown element with a bright green emission line in its spectrum and named the element thallium, from the Greek thallos, a green shoot. Crookes identified the first known sample of helium, in 1895.Crookes turned his attention to the newly discovered phenomenon of radioactivity, achieving the separation from uranium of its active transformation product, uranium-X.

Several scientists, such as William Prout and Norman Lockyer, had suggested that atoms were built up from a more fundamental unit, but they envisioned this unit to be the size of the smallest atom, hydrogen. Thomson in 1897 was the first to suggest that one of the fundamental units was more than 1,000 times smaller than an atom, suggesting the subatomic particle now known as the electron.

was a New Zealand-born British physicist who came to be known as the father of nuclear physics.[2] Encyclopædia Britannica considers him to be the greatest experimentalist since Michael Faraday

Antoine Henri Becquerel was a French physicist, Nobel laureate, and the first person to discover evidence of radioactivity. For work in this field he, along with Marie Skłodowska-Curie and Pierre Curie, received the 1903 Nobel Prize in Physics.

At the end of the 19th century, a number of discoveries were made in physics which paved the way for the breakthrough of modern physics and led to the revolutionary technical development that is continually changing our daily lives.

Rutherford atomic model, also called nuclear atom or planetary model of the atom, description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford.

Robert Andrews Millikan was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electronic charge and for his work on the photoelectric effect.

Sir James Chadwick, CH, FRS was an English physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932.