Question

oppositely charged objects attract each other. this attraction holds electrons in atoms and holds atoms to one another in many compounds. however, ernest rutherford’s model of the atom failed to explain why electrons were not pulled into the atomic nucleus by this attraction. what change to the atomic model helped solve the problem seen in rutherford’s model?
○ bohr’s work with atomic spectra led him to say that the electrons were limited to existing in certain energy levels, like standing on the rungs of a ladder.
○ bohr’s work with cathode rays led him to say that the electrons were located within the mass of positive material, like plums in a pudding.
○ thomson’s work with cathode rays led him to say that the electrons were located within the mass of positive material, like plums in a pudding.
○ thomson’s work with atomic spectra led him to say that the electrons were limited to existing in certain energy levels, like standing on the rungs of a ladder.

Explanation:

1. Analyze each option:

• Option 1: Bohr studied atomic spectra and proposed that electrons exist in specific energy levels (like rungs of a ladder). This explained why electrons don't fall into the nucleus, as they can only occupy certain energy states and don't radiate energy continuously while in those states, solving Rutherford's model's problem.
• Option 2: The "plum - pudding" model is Thomson's, not Bohr's, and cathode rays were related to Thomson's work on discovering electrons, not Bohr's work on energy levels. So this option is incorrect.
• Option 3: Thomson's plum - pudding model was before Rutherford's model and didn't solve the problem of Rutherford's model (electrons not falling into the nucleus). It just described the atom as a positive sphere with electrons embedded, so this option is incorrect.
• Option 4: Thomson didn't work with atomic spectra to propose energy levels for electrons; that was Bohr's work. So this option is incorrect.

Answer:

A. Bohr's work with atomic spectra led him to say that the electrons were limited to existing in certain energy levels, like standing on the rungs of a ladder.