Scientists Flashcards
Democritus
matter consisted of indivisible particles called atoms.
Dalton
“atomic theory” of atoms. He perceived atoms to be solid little spheres.
Arrhenius
discovered the electrical nature of chemical solutions.
Faraday
experimented with electricity running through solutions. Discovered matter had electrical properties.
Kirchhoff
electrical circuits, spectroscopy (emission/absorption line spectra), and the emission of blackbody radiation by heated objects.
Mendeleev
determines there is periodicity of physical and chemical properties of elements in the periodic table.
Crookes
“vacuum tube” called Crookes tube. He discovered that rays with a negative charge flowed from the cathode to the anode in gas discharge tubes. These rays are referred to as cathode rays.
Goldstein
discovered that rays with a positive charge flowed from the anode to the cathode in gas discharge tubes. These are referred to as canal rays.
Röentgen
discovered X-rays and that they had no charge.
Bequerel
discovered radioactivity studying uranium salt.
Thomson
discovered electrons. He determined the charge/mass ratio of the electron. Plum Pudding Model. He did quantitative studies of cathode rays.
Planck
proposed that radiant energy is emitted/absorbed in discrete units called quanta. E = h (h = Planck’s constant = 6.626x10-34 J*s) (λ= frequency)
Einstein
proposed that light or free radiant energy dissociated from all matter was particulate. Light is made of particles, each of which carries a definite amount of energy (quantum). A photon is a quantum of light energy.
Millikan
determined the charge of the electron via the charged oil drop experiment. Mass of an electron = 0.00055 u.
Rutherford
discovered the nucleus conducting the “Gold Foil Experiment”. He proposed the “Nuclear Model”. In 1914 he discovered the lowest charge on an ionized gas particle is from the hydrogen ion.
Soddy
discovered that radioactive decay suggests different atoms of the same element.
Bohr
using Rutherford’s concept of a nuclear atom, and Planck’s Quantum Theory, proposed the “Planetary Model” for atomic structure.
Moseley
determined the charges on the nuclei of most atoms. He realized that the atomic number/number of protons was unique to each element.
Aston
his work with mass spectrometers indicates that there are different masses for some atoms of the same element.
de Broglie
proposed that matter has both particle and wave-like characteristics (wave-particle duality). de Broglie equation: λ = h/mv
Schröedinger
visualized an atom as a positively charged nucleus surrounded by vibrating electron waves. He used mathematical probability to describe the location of electrons in an atom. Electrons are described by four quantum numbers: n, l, ml and ms
Chadwick
discovered the neutron through the bombardment of beryllium.
