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19 Cards in this Set

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  • Back
atom
the smallest particle of an element that can exist either alone or in combination with other atoms
democritus
first to suggest the idea of an atom
DEMOCRITUS ATOM theory
identical in substance
different sizes and shapes
in constant motion
indivisible and eternal
John Daltons Atomic theory 1(1808)
- all matter is composed of extremely small particles called atoms
J D A T 2
-atoms of a given element are identical in Size MAss and other properties, atoms of different elements DIFFER in size mass and other properties
J D A T 3
Atoms cannot be subdivided, created, or destroyed
A+B= AB
J D A T 4
Atoms of different elemts can combine in simple whole number ratios to form chemical compounds ( law of deefinite composition)
2Hs+0s --> 2HsO
J D A T 5
in chemical reactions, atoms are combined, separated, or rearranged
Atomic structure
the identity and arrangement of smaller particles within atoms
electrons
negatively charged subatomic particles
Thompson 1897
identified electron using cathode ray experiment
melikah 1909
calculated mass of electron and determined the charge as being -1.
mass- 9.109 X 10 to the -28
nucleus
positively charged dense central portion of the atom that contains nearly all of its mass but takes up only an insignificant fraction of its volume
Rutherford, Geiger, and Marsden 1908 1909
used gold foil experiments to discover nucleus
proton
subatomis particles that have a positive charge equal in magnitude to the negative charge of an electron and are present in atomic nuclei
mass- 1.673 X 10 to -24 rel mass. 1 amu... charge +1
Rutherford 1919
discovered protons ** same number of protons and electron
neutrons n to the o
electrically neutral, subatomic particles found in atomic nuclei
mass 1.675 X 10^-24
charge 0 neutral
rel mass - 1 amu
chadwick 1932
discovered neutron
element
a substance composed of atoms all of which contain the same # of protons