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Atomic Structure

The size of the nucleus and the electrons are very small, so the atom is mostly composed of empty space
The size of the nucleus and the electrons are very small, so the atom is mostly composed of empty space 

An atom is composed of a nucleus surrounded by an electron cloud. The nucleus consists of a collection of neutrally-charged particles called neutrons and positively-charged particles called protons. Protons and neutrons are called nucleons. The size of the nucleus and the electrons are very small, so the atom is mostly composed of empty space.  The mean free path is the average distance a neutron travels in a medium before interacting with another nucleus.

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