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John Dalton...
... preformed experiments with various chemicals that showed matter seems to consinst of elementary lumpy particles (atoms). -
JJ Thomson...
... discovers electron and proton -
Max Planck...
... showed that when you vibrate atoms strong enoughyou can measure the energy only in discrete units. He called these energy packets, quanta. -
Albert Einstein...
... explained that light absorption can release electrons from atoms, a phenomenon called the "photoelectric effect." -
Robert Andrews Millikan...
... accurately measures the charge of the electron -
Niels Bohr...
... came up with a theory that said the electrons do not spiral into the nucleus. He came up with some rules for what does happen. "Here's some rules that seem impossible, but they describe the way atoms operate, so let's pretend they're correct and use them."
RULE 1: Electrons can orbit only at certain allowed distances from the nucleus.
RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boos -
Ernest Rutherford...
... discovered Protons. Rutherford thought that the negative electrons orbited a positive center in a manner like the solar system where the planets orbit the sun. -
Arnold Sommerfeld (and Niels Bohr)...
... discovered that not only do electrons travel in certain orbits but the orbits have different shapes and the orbits could tilt in the presence of a magnetic field. Orbits can appear circular or elliptical, and they can even swing back and forth through the nucleus in a straight line. -
Wolfgang Pauli...
... predicted that an electron should spin while it orbits around the nucleus. Also, if an electron has a certain set of quantum numbers, then no other electron in that atom can have the same set of quantum numbers. -
Louis de Broglie...
... thought that if light can exist as both particles and waves, why couldn't atom particles also behave like waves? He showed what matter waves would behave like if they existed at all. (Experiments later proved him correct.) -
Erwin Schrödinger...
... thought, 'why not go all the way with particle waves and try to form a model of the atom on that basis?' His theory worked. Called them "psi". -
Max Born...
... thought 'psi' resembled waves of chance. These ripples moved along waves of chance, made up of places where particles may occur and places where no particles occurred. The waves of chance ripple around in circles when the particle appears like an electron in an atomic orbit, and they ripple back and forth when the electron orbit goes straight through the nucleus, and they ripple along in straight lines when a free particle moves through interatomic space. -
Werner Heisenberg...
... formulated that no experiment can measure the position and momentum of a quantum particle simultaneously. This implies that as one measures the certainty of the position of a particle, the uncertainty in the momentum gets correspondingly larger. Or, with an accurate momentum measurement, the knowledge about the particle's position gets correspondingly less.
The visual concept of the atom now appeared as an electron "cloud" which surrounds a nucleus. -
James Chadwick...
... discovered neutron -
Murray Gell-Mann and Yuval Ne'man...
... proposed a method for classifying all the particles then known. The method became known as the Eightfold Way. Gell-Mann thought there existed at least three types of quarks. They have the names, "up," "down," and "strange." From 1974 thru 1984 the theory predicted three more quarks called "charm," "bottom" (or beauty), and "top" (or truth). And each quark has their corresponding anti-quark.
