What are energy levels

set distances were electrons can be sensed.

Explanation:

Energy levels are set distances from the nucleus of the atom where electrons can be sensed. Electrons are small, negatively charged particles in the atom that pass through the positive nucleus in the center. The energy levels are a little like the steps of the stairs. You may stand on one step or the other, but not between the moves. The same thing goes with electrons. 

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metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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