The Atom Flashcards
(13 cards)
What did John Dalton propose about the atom?
He thought of the atom as a solid sphere that could not be divided into smaller parts
Dalton’s model did not include protons, neutrons, or electrons.
What were the first sub-atomic charged particles discovered?
Electrons - tiny, negatively charged particles
Their discovery led to the development of the plum pudding model.
Describe the plum pudding model of the atom.
A cloud of positive charge with negative electrons embedded in it
Protons and neutrons had not yet been discovered.
What was the purpose of the alpha scattering experiment?
To investigate the structure of the atom by firing alpha particles at gold foil
The foil was only a few atoms thick.
What surprising result was found in the alpha scattering experiment?
Some alpha particles bounced back and many were deflected
This indicated that the positive charge and mass of an atom are concentrated in a small space.
What did scientists conclude about the nucleus from the alpha scattering experiment?
The positive charge and mass of an atom must be concentrated in a small space at its center
They called this space the nucleus.
What model replaced the plum pudding model?
The nuclear model
This model suggested that electrons orbit the nucleus.
What did Niels Bohr contribute to atomic theory?
He calculated that electrons must orbit the nucleus at fixed distances
These orbits are called shells or energy levels.
What is the radius of an atom?
1x10^-10 m
Nuclei are around 10,000 times smaller than atoms.
What is the relative mass of protons and neutrons?
Both have a relative mass of 1
Electrons have a relative mass considered as 0.
What charge does a proton have?
Opposite charge to an electron
Protons and neutrons are located in the nucleus.
Who discovered the neutron?
James Chadwick
His experiments provided evidence for a particle with no charge.
Where are protons and neutrons located in the atom?
In the nucleus
Electrons orbit the nucleus in shells.
