The History of the Atom Flashcards
Atomic Structure and the Periodic Table (13 cards)
Who described atoms as solid spheres at the start of the 19th century?
John Dalton
Dalton’s model suggested that different spheres made up different elements.
What did J.J. Thomson conclude about atoms in 1897?
Atoms weren’t solid spheres and contain negatively charged particles called electrons
This led to the ‘plum pudding model’ of atomic structure.
What does the ‘plum pudding model’ depict?
The atom as a ball of positive charge with electrons embedded in it.
What experiment did Ernest Rutherford conduct in 1909?
Alpha particle scattering experiment
This involved firing positively charged alpha particles at a thin sheet of gold.
What was the expectation of Rutherford’s experiment based on the plum pudding model?
Particles would pass straight through or be slightly deflected.
What was the outcome of Rutherford’s alpha particle scattering experiment?
Some particles were deflected more than expected, and a small number were deflected backwards.
What did Rutherford propose to explain his experimental results?
The nuclear model of the atom
This model includes a tiny, positively charged nucleus at the center.
What surrounds the nucleus in Rutherford’s nuclear model?
A cloud of negative electrons.
What did Niels Bohr suggest about electron arrangement?
Electrons are confined in fixed shells around the nucleus.
What is a key feature of Bohr’s model of the atom?
Electrons orbit the nucleus in fixed distances and are not found in between shells.
What particles did further experiments reveal in the nucleus?
Protons
These particles have the same charge as a hydrogen nucleus.
Who provided evidence for neutrons in the nucleus?
James Chadwick.
What resulted from the discovery of neutrons?
A model of the atom that closely resembles the modern-day accepted version.
