Answer:
Overall charge = -3
Step-by-step explanation:
The atom of every chemical element is its smallest indivisible part. However, this atom further consists of subatomic particles namely: proton, electron, and neutron. The proton and electron are the positively charged and negatively charged particle respectively.
In a neutral atom, the amount of proton and electrons in that atom equates. However, the amount of electron and proton present in an atom determines the charge of that atom. For example, in this question, an atom is said to contain 17 protons, 17 neutrons and 20 electrons.
Since the negatively charged electrons (20) are more than the positively charged protons (17) by 3, hence, the net charge is -3.