A single atom of an element has 21 neutrons, 20 electrons, and 20 protons. Which element is it?

An element is identified by its number of protons, called its atomic number. With 20 protons, the atom has atomic number 20, which is calcium (Ca). The 21 neutrons affect its isotope, and the 20 electrons make it neutral, but neither changes the element’s identity.

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