Question

The pair of elements which on combination are most likely to form an ionic compound is:
(A) $Na$ and $Ca$
(B) $K$ and $O$
(C) $O$ and $Cl$
(D) $Al$ and $I$

Answer 1

Hint: Bond in the molecule is defined as the force of attraction between the molecules which can bind the atoms in the molecule. Bond can be formed by sharing of electrons or by electrostatic force of attraction.

Complete step by step solution:
First of all let us talk about what is bonding and their types.
There are mainly three types of bonds. Ionic, covalent, hydrogen and metallic bonds.
Ionic bond: In this type of bond one atom of the molecule will lose its electrons and the other atom will gain the electrons. The atom which will lose the electrons will attain a positive charge (known as cation) while the atom which will gain the electron attain a negative charge(known as anion). For example: Calcium oxide, in this molecule calcium acts as cation while oxygen acts as anion.
Covalent bond: In this type of bond one atom of the molecule will share its electrons with the other atoms of the same molecule. For example: ethane, methane etc. In these types of molecules carbon and hydrogen share their electrons with each other.
Hydrogen bond: In this type of bond one atom is hydrogen and the other atom is oxygen, nitrogen or fluorine. The bond between these atoms is known as hydrogen bond. For example: water.
Metallic bonds: They are formed between atoms of metals. For example: alloy (brass or bronze).
We have combinations i) sodium and calcium we know that they both are metals so cannot form ionic bonds.
ii) Potassium and oxygen in this combination potassium is metal and hence can donate the electrons while oxygen is non- metal and hence can accept the electrons. Hence they can form ionic compounds.
iii) Oxygen and chlorine both are non-metals and hence not able to form ionic compounds.
iv) Aluminium and iodine also are not able to form ionic compounds because of large differences in the size.
Hence option B is correct.

Note:
Hydrogen bonds are of two types: Intermolecular and intramolecular hydrogen bonds.
Intermolecular hydrogen bonds: They are formed between two or more different molecules of the same or different types.
Intramolecular hydrogen bonds: They are formed within a molecule.