1.5: History Of The Atom Flashcards
(12 cards)
What should you know after studying the history of the atom?
You should know how and why the atomic model has changed over time and that scientific theories are revised or replaced by new ones in light of new evidence.
Who first linked the idea of atoms to experimental evidence?
John Dalton linked the idea of atoms to strong experimental evidence in the early 1800s.
What did Dalton suggest about atoms?
Dalton suggested that substances were made up of tiny, hard spheres called atoms, each with its own mass, and that they could not be divided.
How did Dalton describe chemical reactions?
Dalton suggested that atoms rearranged themselves and combined with other atoms in new ways during chemical reactions.
What did J.J. Thomson discover at the end of the 1800s?
J.J. Thomson discovered the electron, a tiny negatively charged particle with a mass about 2000 times smaller than the lightest atom.
What was Thomson’s experiment about?
Thomson applied high voltages to gases at low pressure and found that beams of particles were attracted to a positive charge, indicating they were negatively charged.
What model did Thomson propose for the atom?
Thomson proposed the plum pudding model, where electrons are embedded in a cloud of positive charge.
What did Geiger and Marsden discover about the atom?
Geiger and Marsden discovered that the positive charge in an atom is concentrated at a tiny spot in the center, leading to the proposal of the nuclear model.
What did Rutherford suggest about electrons?
Rutherford suggested that electrons orbit around a dense positively charged nucleus.
What did Niels Bohr revise in the atomic model?
Niels Bohr proposed that electrons orbit the nucleus at set distances in fixed energy levels.
What evidence led to the discovery of neutrons?
James Chadwick provided evidence for the existence of neutrons in 1932, explaining the missing mass in atoms.
What are the key points about the history of atomic models?
Ideas about atoms have changed over time based on new evidence from experiments by Dalton, Thomson, Rutherford, and Bohr.
