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Democritus 450 BC; "atomos" -Greek for indiisible, matter consists of elementary solid sphere particles
John Dalton 1803; Atomic theory- elements made of atoms, which are indivisible particles, atoms of same element are identical
JJ Thompson 1897; electrons were like plums embedded in a positively charged "pudding" this it was called PLUM PUDDING MODEL; found the electron
Rutherford 1911; from the Gold Foil experiment; atom is mostly empty; small dense, positive nucleus @ center; alpha particles are deflected if they get close enough; electrons in empty space; NUCLEAR MODEL
Bohr 1913; electrons found ONLY in specific orbits around the nucleus; PLANETARY MODEL
Schrodinger 1926; mathematically described the behavior of electrons in atoms; locations based on probability; QUANTAM MECHANICAL MODEL
James Chadwick 1932; using alpha particles discovered a meutral atomic particle with a mass close to a proton: neutron
Protons and neutrons are ___ fundamental particles NOT
In a neutral atom, the number of _______ = the number of _________. protons, electrons
If there is not an equal number of protons and electrons it is an ___. ion
Do all atoms of an element have the same masses? no
isotope atom of the same element that differs in the number of neutrons
atomic mass average of all the natural isotopes of that element
Z= ______ _____ atomic number
A= ____ ______ mas number
Radioactivity process by which nuclei emit particles and rays
radiation the penetrating rays emitted by a radioactive source
alpha particles helium nucleus (+2 charge, large mass)
beta particles high speed electron
gamma rays high energy light (photon)
Nuclear decay need stable ratio of neutrons to protons; neutron-to-proton ratio determines type of decay that occurs
transmutation conversion of an atom of one element to an atom of another element
Alpha emission 4:2 He
Beta emision increases # protons, decreases # neutrons, mass # same atomic # +1
Positron emission proton->neutron, mass # same atomic # -1
electron capture proton-> neutron, mass # same, atomic # -1 electron captured
Two types of nuclear energy fission and fusion
fission splitting a nucleus into two or more smaller nuclei by neutorn bombardment
fusion combining of two nuclei to form one nucleus larger mass
Created by: AlanaR