1.1 Describe how the Dalton model of an atom has changed over time because of the discovery of subatomic particles Flashcards
Who published the three-part atomic theory in 1803?
John Dalton published his own three-part atomic theory.
What is the first part of Dalton’s atomic theory?
All substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed.
What is the second part of Dalton’s atomic theory?
Atoms of the same element are exactly alike, and atoms of different elements are different.
What is the third part of Dalton’s atomic theory?
Atoms join with other atoms to make new substances.
What was later proven incorrect about Dalton’s theory?
Much of Dalton’s theory was correct, but some of it was later proven incorrect and revised as scientists learned more about atoms.
What experiment did J.J. Thomson conduct in 1897?
Thomson used a cathode-ray tube to conduct an experiment.
What error in Dalton’s atomic theory did Thomson identify?
Atoms can be divided into smaller parts.
What did Thomson conclude about the particles in his experiment?
The beam moved away from the negatively charged plate and toward the positively charged plate, indicating that the particles must have a negative charge.
What model of the atom did Thomson propose?
Thomson proposed the ‘plum-pudding’ model, in which negative electrons are scattered throughout soft blobs of positively charged material.
What experiment did Ernest Rutherford conduct in 1909?
Rutherford shot a beam of positively charged particles into a sheet of gold foil.
What were the results of Rutherford’s gold foil experiment?
Most particles continued in a straight line, but some were deflected to the sides and a few bounced straight back.
What new model did Rutherford develop based on his experiment?
Rutherford developed a new model stating that most of the atom’s mass is found in a region in the center called the nucleus.
What did Rutherford’s model say about the structure of the atom?
In Rutherford’s model, the atom is mostly empty space, and the electrons travel in random paths around the nucleus.
