History of the Atom - GCSE Chemistry

Front

Who proposed the atomic theory in 1803?

Back

John Dalton

Front

What are the three key ideas of Dalton's atomic theory?

Back

1. Matter is made of atoms which cannot be created, destroyed, or divided. 2. Atoms of the same element are identical, and atoms of different elements are different. 3. Different atoms combine to form new substances.

Front

What is the plum pudding model?

Back

A model proposed by J.J. Thomson where negative electrons are spread throughout soft globules of positively charged material.

Front

Who discovered the electron and when?

Back

J.J. Thomson in 1897.

Front

What did Rutherford's gold foil experiment demonstrate?

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It showed that most of an atom's mass is concentrated in a central nucleus, contradicting the plum pudding model.

Front

What is the nuclear model of the atom?

Back

A model where the atom consists mainly of empty space with a central nucleus and electrons orbiting around it.

Front

Who developed the Bohr model and what does it propose?

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Niels Bohr in 1913; it proposes that electrons orbit the nucleus in fixed shells or orbitals.

Front

What did James Chadwick discover in 1932?

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The neutron, a neutral particle within the nucleus.