P4-Atomic Structure Flashcards
Who created the Plum pudding model?
JJ Thomson.
What did JJ Thomson discover?
Particles called electrons that could be removed from atoms. Somewhat disapproving Dalton’s theory. Thomson suggested atoms were spheres of positives charge with tiny negative electrons stuck in them.
What was John Dalton’s theory?
Agreed with Democritus that matter was made up of tiny spheres (“atoms”) that couldn’t be broken. But reckoned each atom was made up of different “atoms”.
What experiment was created by Rutherford?
Firing a beam of alpha particles at thin gold foil - called alpha scattering experiment.
How was the nucleus confirmed/discovered?
During the alpha scattering experiment a few particles were deflected back, they realised that most of the mass of the atom must be concentrated at the centre in a tiny nucleus. The nucleus must also have a positive charge, since it repelled the positive alpha particles.
What did Rutherford replace the Plum Pudding model with?
The nuclear model.
What did the nuclear model develop into?
The current model of the atom.
What was Niels Bohr’s theory?
Said that electrons orbiting the nucleus do so at certain distances called energy levels.
What did James Chadwick prove?
Proved the existence of the neutron, which explained the imbalance between the atomic and mass numbers.
What are isotopes?
Different forms of the same element.
What is the mass number?
Is the number of protons + number of neutrons in its nucleus.
What are alpha particles?
Helium Nuclei. An alpha particle is two neutrons and two protons (like a helium particle).
What are Beta particles?
High-speed electrons. Is simply a fast-moving electron released by the nucleus. Beta particles have virtually no mass and a charge of -1.
Describe gamma rays waves?
Are EM waves with a short wavelength.
What are gamma rays?
Are waves of electromagnetic radiation released by the nucleus.
