Atomic Structure
•A brief summary
Models of The Atom
The Dalton Model (1810)
• Atoms are hard
spheres( i.e. marbles
or grains of sand)
Didn’t explain:
1. how atoms stick
together (bonds)
2. how atoms of each
element are different
Models of The Atom
The Plum Pudding Model
• Proposed by J.J.Thomson
(~1897)
• Atoms contained
negatively-charged
particles called corpuscles
which were embedded in a
sphere of positive charge
• Atoms were mostly empty
space
Thomson’s experiment
Models of The Atom
Rutherford Model (aka:
nuclear model) ~1911
• The nucleus, which is at
the center of the atom,
contains protons
(positively charged) and
all of the atom’s mass
• Electrons move around
the nucleus.
Rutherford’s Experiment
Alpha particle scattering experiment
Rutherford’s experiment
(a) The results that the metal foil
experiment would have yielded if the
plum pudding model had been correct
(b) Actual results