Question

The electronegativities of elements A and B are 1.2 and 3.4 units respectively. The type of bond connects A and B in compound AB is:
(A) Covalent
(B) Ionic
(C) Coordinate covalent
(D) Polar covalent

Answer 1

To answer this question we should be aware of the definition of types of bond that are mentioned in option portion and understand how these bonds are formed. This helps us find the answer within no time.

Complete Solution :
Chemical bonding between two molecules, ions or atoms are due to electrostatic force of attraction between them or due to sharing of electrons between them leads to formation of bond and enables the formation of chemical compounds.

Now, let's look into each option for better understanding.
- The option A is covalent bond. The chemical bonding formed by sharing of electrons between a pair of atoms or molecules is known as covalent bond. The covalent bonds are formed when the electronegativity difference between the atoms that are sharing electrons are either infinitesimally small that it can be neglected or the electronegativity is 0. The electronegativity must be 0 for 100% covalent bond so, this option is the wrong answer.

- The option B is an ionic bond. The ionic bond is formed by the transfer of one or more electrons from one atom to another. In ionic compounds the ions are linked together by electrostatic force of attraction. Ionic bonds are highly polar.
Let's see the electronegativity difference between given atom A and B
A = 1.2
B = 3.4
$\Delta E.N = {{E}_{B}}-{{E}_{A}}$
$\Delta E.N = 3.4-1.2$
$\Delta E.N$ = 2.2
Whenever the electronegativity difference is greater than 1.7 then, the compound is said to be more ionic.
Thus from the above discussion it is evident that option B is the correct answer.

- Option C is coordinate covalent bond. Coordinate bond is established by one side sharing of an electron pair between the linked atoms. It is a semi polar compound because the covalent character is more. This option is not the correct answer.

- Option D is polar covalent bond. As mentioned in explanation of option A. The covalent bonds are formed when the electronegativity difference between the atoms that are sharing electrons are infinitesimally small that it can be neglected. Thus, this option is the wrong answer,
So, the correct answer is “Option B”.

Note: The covalent compounds will be either polar or nonpolar, the ionic compounds are highly polar and Coordinate covalent compounds are semi polar. In this question only electronegativity values of atoms that form a bond is given. We might confuse between coordinate covalent bonds that are ionic. Let's make it clear whenever the electronegativity difference is more than 1.7 then the compound is ionic.