What is the origin of the word atom?
The word atom comes from the ancient Greek term atomos, meaning uncuttable. Ancient philosophers like Leucippus and his student Democritus proposed that all matter consists of indivisible units called atomos.
Questions about Atom
Short answers, pulled from the story.
When did J. J. Thomson discover electrons in the atom?
In 1897, J. J. Thomson discovered that cathode rays could be deflected by electric and magnetic fields. He measured these particles to be 1,700 times lighter than hydrogen and showed that atoms were not indivisible as scientists had thought.
How does the Bohr model explain electron stability in an atom?
In 1913, Niels Bohr proposed a new model where electrons could only do so in a finite set of orbits. Electrons could jump between these orbits only in discrete changes of energy corresponding to absorption or radiation of a photon, which explained why electron orbits are stable.
What is the uncertainty principle formulated by Werner Heisenberg for the atom?
In 1927, Werner Heisenberg formulated the uncertainty principle stating it is mathematically impossible to obtain precise values for both position and momentum of a particle at a given point in time. For a given accuracy in measuring a position one could only obtain a range of probable values for momentum.
How large is the nucleus compared to the radius of an atom?
The radius of a nucleus is approximately equal to 1.2 femtometres times the cube root of the total number of nucleons. This is much smaller than the radius of the atom which is on the order of 105 femtometres.