The number of electrons in an ion with 16 protons and an ionic charge of 2- is

In a given neutral atom, actually the number of protons and electrons are equal. So ideally in this case the number of electrons should also be 16. However we have an ionic charge of negative 2. Since it is negative, this means there are 2 more electrons than protons, hence the answer is:

18 electrons

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.