Here's why:
* Chlorine's atomic number is 17, meaning it has 17 protons in its nucleus.
* Protons have a positive charge (+1).
* Atoms are electrically neutral. To achieve neutrality, chlorine must also have 17 electrons.
* Electrons have a negative charge (-1).
* The electron cloud is the region around the nucleus where electrons are found.
Therefore, the total charge of the electron cloud in chlorine-37 is -17. The isotope number (37) doesn't affect the number of electrons in a neutral atom.
