Scientists Flashcards
Democritus (460 B.C.-370 B.C.)
Democritus is a Ancient Grecian philosopher usually the one credited with first imagining the atom. he said that an atom is a tiny inadvisable particle and that it was the smallest part of the universe. we have since discovered that atoms are divisible.
John Dalton (1766- 1844)
Dalton published the first fully scientific model of an atom. he said that atoms combine together in a whole number of ratios to form the compounds that different substances are made of.
J. J. Thomson (1856-1940)
Thomson performed a series of experiments that produced beams of electrons inside a glass tube. he made a new atomic model called the plum pudding model. Thomson said that atoms were made up of a cloud of positively charged material with negatively charged particles embedded in it.
Ernest Rutherford (1871-1937)
in 1909 Rutherford experimented with firing small positively charged particles at a thin foil made of pure gold. he concluded that positive charge is concentrated in the center not spread out as Thomson had proposed. he called this central concentration the nucleus. he also said that electrons were outside the nucleus surrounding it and most of the atom was empty space .
Niels Bohr (1885-1962)
he was the first to propose that electrons orbit the nucleus. Bohr said that orbits represent different energy levels for electrons. lower energies were closer to the nucleus and higher energies were farther out.
James Chadwick (1891-1974)
Chadwick was the first one to imagine a neutron. he said that the neutron has mass and that is has no electric charge.
Aristotle (384 B.C.-322 B.C.)
Aristotle was a Grecian philosopher. his ideas about physics were based on philosophical reasoning and not on experimentation. Aristotle taught that all objects have natural motion (part of their telos) that requires heavy things to go down and light things to go up. he also held that force was required to maintain motion because without a force it was natural for objects to stop moving. and he further argued that heavy objects fall faster than lighter objects, in proportion to their weights.
Galileo Galilei (1564-1642)
Galileo studied space. his studies led him to believe that the earth orbited the sun not vice-versa. this belief got him in trouble with the church and he spent several years on house arrest.
Isaac Newton (1643-1727)
Newton publish the Principia Mathimatica. the Principia stated Newton’s understanding of science. Newton’s laws of motion are a theoretical model for the mechanical world. his laws are still used today.
