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Chemistry 1.3 (The history of the atom (1909 Ernest Rutherford (+ student…
Chemistry 1.3
The history of the atom
start of 19th century John Dalton
solid sphere
1897 JJ Thomson
not solid spheres
small negatively charged particles electrons
plumb pudding model
ball of positive charge with electrons stuck in it
1909 Ernest Rutherford (+ student Ernest Marsden)
alpha particle scattering experiment
nuclear model
more particles deflected than expected
mass concentrated
Niels Bohr's
electrons orbit the nucleus in fixed shells
James Chadwick
evidence of neural particles neutrons
protons discovered
Electronic structure
lowest energy levels filled first
1st shell = 2 2nd shell = 8 3rd shell = 8
occupy shells
goal is to have a full outer shell
atoms react to have a full outer shell
modern periodic table
element with similar properties are in the same columns
group number is how many electrons on its outer shell
metals left
non metals right
development of the periodic table
1800s arranged by atomic mass
properties were not taken into account
1869 Dmitri Mendeleev
left gaps for undiscovered elements
order of atomic mass
some elements swapped because of properties
gaps allowed elements to stay in the right group