What is an atom or group of atoms with an electric charge called

Ion

Explanation:

An atom is generally neutral, since its number of protons in the nucleus is equal to the number of electrons around the nucleus: since proton and electrons have opposite charge (but equal in magnitude), the total charge of the atom is zero.

However, sometimes atoms can gain or lose electrons: when this happens, they are called ions. In particular:

- When an atom loses one (or more) electrons, it remains with an excess of positive charge, so it is called positive ion

- When an atom gains one (or more) electrons, it remains with an excess of negative charge, so it is called negative ion

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide