17 terms

Structure of the Atom

History of atomic models and structure of the atom
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Proton
positively charged subatomic particle with mass of 1u. Located in the nucleus.
Electron
negatively charged subatomic particle with mass of 1/1840 u. Located outside the nucleus in orbitals.
Neutron
neutral subatomic particle with mass of 1 u. Located in the nucleus.
Atoms
the smallest particle of an element.
Nucleus
the dense, center of an atom. has a positive charge. made up of protons and neutrons.
subatomic
particles that are smaller than an atom
net charge
the difference in the positive charge due to protons and the negative charge due to electrons.
atomic number
the number of protons in an atom. Determines the identity of the element.
mass number
the total number of protons and neutrons.
isotopes
atoms with the same number of protons, but different number of neutrons and a different mass number.
average atomic mass
the weighted average of all the isotopes that are present in an element.
Democritus
Greek philospher that originiated the idea of the atom (atomos). Matter is made up of tiny indivisible particles.
John Dalton
Matter is made up of particles called atoms. Atoms of identical elements are all identical. Atoms combine in whole number ratios to form compounds. Atoms are rearraged during a chemical reaction but no new atoms are created.
J.J. Thomson
Plum Pudding Model. Atoms consist of electrons in a "pudding" of positive charge. Experiment with cathode ray tube found that atoms contain negatively charged particles called electrons.
Ernest Rutherford
Gold foil experiment. Atoms are mostly empty space with a small, dense positively charged nucleus.
Neils Bohr
electrons exist in circular orbits of specified energy around the nucleus.
Ion
An atom with a net charge