Atomic Theory Timeline Flashcards
What did Ancient Greeks believe the universe was made of?
The universe was made of earth, water, air, fire, and aether, and these elements followed a specific order.
What was Democritus’ theory about matter?
Democritus suggested that matter couldn’t be divided infinitely and was made of small, indivisible particles called ‘atoms.’
What was John Dalton’s atomic theory (1808)?
John Dalton’s atomic theory stated: 1) Atoms are tiny, invisible particles. 2) Atoms of the same element are identical. 3) Atoms of different elements are different. 4) Compounds are formed by combining atoms.
What did J.J. Thomson discover in 1897?
J.J. Thomson discovered electrons using cathode rays, showing that atoms were made of smaller particles.
What was J.J. Thomson’s atomic model?
J.J. Thomson’s atomic model, called the ‘Plum Pudding’ model, depicted negative electrons surrounded by a positively charged sphere.
What did Ernest Rutherford discover in 1911?
Ernest Rutherford, through the gold foil experiment, discovered that atoms have a dense, positive nucleus made of protons.
What was Rutherford’s atomic model?
Rutherford’s atomic model suggested that most of the atom is empty space with a small, dense nucleus at the center.
What did Neils Bohr propose in 1913?
Neils Bohr proposed that electrons orbit the nucleus in specific shells, leading to the modern atomic model.
What did James Chadwick discover?
James Chadwick discovered the neutron.
