Hint: As we know that protons are positively charged, electrons are negatively charged. If we have to find the number of neutrons, we will subtract the atomic number from the mass number. And we can easily find the electrons, neutrons and protons.
Complete Solution :
- As we all know that atomic number denotes the total number of protons present in the nucleus of an atom.
- As we know that oxygen atom is having atomic number eight. It is found that the number of protons is equal to the atomic number. This means that the nuclei of all oxygen atoms have eight protons. It is found that a neutral oxygen atom will also have eight electrons.
- In an oxygen ion that has a -2 charge, the number of protons present is eight, but the total number of electrons is 10. Due to this oxygen ion is having an octet of valence electrons.
- Hence, we can conclude that there are 8 protons and 10 electrons in an oxygen ion that has a -2 charge.
Note: - We should note that the total number of neutrons present in the nucleus is equal to the difference between the atomic number and the mass number of an atom.
- As we know that the mass number of any atom is basically equal to the addition of the protons and neutrons that are present in the nucleus.