2.41. Rutherford’s Atomic Model http://www.ck12.org
2.41 Rutherford’s Atomic Model
- Explain how Ernest Rutherford discovered the nucleus of the atom.
- Describe Rutherford’s planetary model of the atom.
Thom is shooting baskets. He’s trying to hit the backboard so the ball will bounce off it and into the basket. If only
the backboard was bigger! It would be a lot easier to hit. If the ball misses the backboard, it will just keep going and
Thom will have to run after it. Believe it or not, the research that led to the discovery of the nucleus of the atom was
a little like shooting baskets.
Narrowing Down the Nucleus
In 1804, almost a century before the nucleus was discovered, the English scientist John Dalton provided evidence
for the existence of the atom. Dalton thought that atoms were the smallest particles of matter, which couldn’t be
divided into smaller particles. He modeled atoms with solid wooden balls. In 1897, another English scientist, named
J. J. Thomson, discovered the electron. It was first subatomic particle to be identified. Because atoms are neutral in
electric charge, Thomson assumed that atoms must also contain areas of positive charge to cancel out the negatively
charged electrons. He thought that an atom was like a plum pudding, consisting mostly of positively charged matter
with negative electrons scattered through it.
The nucleus of the atom was discovered next. It was discovered in 1911 by a scientist from New Zealand named
Ernest Rutherford, who is pictured inFigure2.77. Through his clever research, Rutherford showed that the positive
charge of an atom is confined to a tiny massive region at the center of the atom, rather than being spread evenly
throughout the “pudding” of the atom as Thomson had suggested. You can watch a video about Rutherford and his
discovery at this URL: