Question

Oxygen atom has 8 electrons and 8 protons. So oxide ion will have
A. 6 protons, 8 electrons
B. 8 protons, 10 electrons
C. 6 protons, 10 electrons
D. 8 protons, 8 electrons

Answer 1

Hint: Oxygen atom has the atomic number 8 and it has incomplete octet. Since it belongs to the category of non-metals, it tries to achieve its stable configuration by gaining electrons and so it forms its anion which is called oxide ion.


Complete step by step solution:
-According to lewis rule, every atom tries to achieve the electronic configuration of the noble gases. This can be done either by losing or gaining electrons which forms ionic bonding between the atoms or by sharing of electrons which forms covalent bonding.
-When an atom combines with another atom as a result of ionic bonding, the two different species formed which have their octet complete are called the ions. Among them, one ion has an excess of electrons which is called anion and one ion has deficiency of electrons which is called cation.
-Cation is formed when an atom loses its electrons to attain the noble gas electronic configuration in order to become stable. Anion is formed when an atom gains electrons to attain the noble gas electronic configuration in order to become stable.
-Oxygen atom has the atomic number 8. Atomic number gives the information about the number of protons as well as the number of electrons. So we can say that
Atomic number = no. of electrons = no. of protons
-So we see that there are 8 electrons and 8 protons in an oxygen atom. We know that every atom always tries to complete its octet by gaining or losing electrons in order to become stable. Oxygen atom belongs to group 16. So it has 6 valence electrons in its outermost shell. Thus, it is easier to gain 2 electrons to complete its octet rather than lose 6 electrons.
-Oxygen atoms already had 8 electrons. If 2 more electrons are added to complete the octet of the ion, the total number of electrons becomes 8+2=10. No change occurs in the number of protons because the protons are located in the nucleus of the atom. So they remain in the nucleus itself and the oxygen ion will also have 8 protons only.

Therefore the correct option is B. 8 protons, 10 electrons


Note: Atomic number tells us about the number of protons and number of electrons while the atomic mass tells us about the number of protons and number of neutrons. If we know both the atomic mass and the atomic number, we can find all the number of protons, electrons and neutrons for any atom.