Does lightning always strike the ground?
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In atoms and molecules the negatively-charged electrons are attracted to the positively charged nucleus. It takes a considerable amount of energy to remove an electron from an atom or molecule. The electric fields produced by thunderclouds have enough energy, and so they can pull an electron from an atom, creating a positively charged atom, or ion, and an electron that is free to move.
Although most people think of lightning when it goes between Earth and clouds, the most common type of lightning occurs inside and between thunderclouds. It is usually easier for lightning to jump between the clouds than it is for it to jump from the clouds to Earth. As a result, only one quarter of all lightning strikes actually strike the ground.