Question

The electronegativities of a few elements are given below. Choose the pairs which form ionic bonds. $$\begin{array}{cc}Element& Electronegativity\\ Lithium\left(Li\right)& 0.98\\ Sodium\left(Na\right)& 0.93\\ Flourine\left(F\right)& 3.98\\ Oxygen\left(O\right)& 3.44\\ Phosphorous\left(P\right)& 2.19\end{array}$$

• A. Lithium and oxygen
• B. Sodium and flourine
• C. Phosphorous and flourine
• D. Sodium and oxygen

Answer 1

Answer: (A), (B), (D)

The correct options are
A Lithium and oxygen
B Sodium and flourine
D Sodium and oxygen

An ionic bond is formed by the transferring of electrons from a metal to a non-metal. For ionic bond formation, the difference in the electronegativities of the constituent atoms is more than 1.9.

Among the given elements difference of electronegativity are as follow:

$\bullet$ Phosphorous and fluorine = 3.98 - 2.19 = 1.79

$\bullet$ Lithium and oxygen = 3.44 - 0.98 = 2.46

$\bullet$ Sodium and oxygen = 3.44 - 0.93 = 2.51

$\bullet$ Sodium and flourine = 3.98 - 0.93= 3.05

Hence, lithium and oxygen, sodium and oxygen, sodium and fluorine form ionic bonds.

While, phosphorous and fluorine form a covalent bond, because
the electronegativity difference between phosphorous and fluorine is 1.79, which is less than 1.9.