Explain the plum pudding model.

The plum pudding model states that the atom has negatively charged electrons spaced throughout the positively charged atomic sphere.

Expert Answers

An illustration of the letter 'A' in a speech bubbles

J. J. Thomson's discoveries contributed to our overall understanding of atoms, but it should be mentioned that his atomic model is not correct by current understanding.

It is probably best to start around 400 BC with Greek philosopher Democritus. He is often credited with starting atomic theory, because he believed...

See
This Answer Now

Start your 48-hour free trial to unlock this answer and thousands more. Enjoy eNotes ad-free and cancel anytime.

Get 48 Hours Free Access

J. J. Thomson's discoveries contributed to our overall understanding of atoms, but it should be mentioned that his atomic model is not correct by current understanding.

It is probably best to start around 400 BC with Greek philosopher Democritus. He is often credited with starting atomic theory, because he believed that everything in existence is made of small, invisible, and indestructible particles.

About 2,200 years would have to pass before Democritus's ideas would be added to. In 1803, chemist John Dalton further developed our understanding of the atom. He discovered that different elements have different chemical properties as well as discovered that atoms of the same element contain the same chemical properties.

Another 100 years would have to pass to get to J. J. Thomson and his plum pudding model. J. J. Thomson is credited with discovering the electron. Thomson's work involved experimentation with cathode rays. He discovered that the rays produced in a discharged tube were attracted to positively charged metal plates. Those same rays were also repelled by negatively charged plates.

From this experiment, Thomson recognized that the rays have to be negatively charged, and that led to him realizing that atoms contain negative charges. Thomson had discovered that atoms were not indivisible but made of smaller parts. Thomson envisioned the internal structure of an atom like a bowl of plum pudding. He imagined that the inside of an atom was a sphere of positive charge with negatively charged particles randomly spread throughout the positive charge in the same way that plums would be spread throughout pudding.

It was only a few years later that the plum pudding model was shown to be incorrect. Rutherford showed that atoms are mostly empty space with a positively charged nucleus in the middle. Bohr contributed to atomic theory by explaining that electrons move around the nucleus in orbits and different levels. This isn't entirely correct, but his orbit levels are still taught in chemistry classes today, because it is an effective model to teach about atoms and energy levels. Current atomic theory shows that electrons exist in clouds of probability, and that model was put forth by Schrödinger.

Approved by eNotes Editorial Team