Question

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Which of these atom model discoveries is out of order?

a. Electron discovered and then electron energy levels
b. Nucleus discovered and then the theory of electron clouds
c. Belief in atoms and then the discovery of electrons
d. Discovery of the nucleus and then the discovery of the electron

Answer 1

d. Discovery of the nucleus and then the discovery of the electron

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The correct chronological order of these discoveries goes:

• The belief in atoms (atomic theory), the discovery of the electron, the realization of electron energy levels or shells, followed by the discovery of the nucleus which led to the concept of electron clouds.

Therefore, option d is out of order because the discovery of the electron occurred before the nucleus was identified.