Question

The valency of sulphide and oxide ions is:
A.-2
B. -3
C. -4
D. -5

Answer 1

Hint: Valency can be called as the combining power that an element possesses. It is actually the combining capacity an element has, so that it gets converted into a compound. Losing an electron will result in positive charge, whereas gaining an electron will result in negative charge.

Complete step by step solution:
In order to answer our question, we need to learn about the structure of atoms. Let us discuss some of the important terms related to atomic structure.
Nucleus: In an atom, the mass and positive charge is centrally located in an extremely small region called nucleus. The volume of the nucleus can be considered negligible when compared to the total volume of the atom. The radius of the atom is about ${{10}^{-10}}$ m and the radius of the nucleus is ${{10}^{-15}}$m. Both protons and neutrons together are called nucleons.
Atomic number: It is equal to the number of protons present in the nucleus of an atom. Atomic number is designated by the letter 'Z'. In case of neutral atoms, atomic number is equal to the number of protons and even equal to the number of electrons in their orbits.
Mass number: It is equal to the sum of the electrically neutral neutrons (n) and positively charged protons (p). Mass number of an atom is designated by the letter 'A'.
Isotopes: Those atoms which have atomic number same but different mass number are called isotopes. Isotopes have the same number of electrons, protons, but they vary in the number of neutrons.
Now let us come to our question. Now, both the sulphide ion and oxide ion are present as ${{S}^{2-}}$ and ${{O}^{2-}}$ respectively. Hence they have a valency of -2.

So, our correct answer for this question will be option A.

NOTE: It is to be noted that although isotopes have differences in the number of neutrons, however isotopes have the same chemical behaviour, because the number of electrons remains the same. In the case of ions, the atomic number is equal to the proton but not equal to the number of electrons.