What is an ionic bond? With two suitable examples the difference between an ionic and a covalent bond?
Ionic bond The bond formed, as a result of the electrostatic attraction between the positive and negative ions was termed as the electrovalent bond or ionic bond. e.g., the formation of NaCl from sodium and chlorine can be explained as
$$\underset{[\mathrm{Ne}] 3 \mathrm{~s}^1}{\mathrm{Na}} \longrightarrow \underset{[\mathrm{Ne}]}{\mathrm{Na}^{+}}+\mathrm{e}^{-}$$
$$\underset{[\mathrm{Ne}] 3 s^2 3 p^5}{\mathrm{Cl}}+\mathrm{e} \longrightarrow \underset{[\mathrm{Ne}] 3 s^2 3 p^6 \text { or }[\mathrm{Ar}]}{\mathrm{Cl}^{-}}$$
$$\mathrm{Na}^{+}+\mathrm{Cl}^{-} \longrightarrow \mathrm{NaCl} \text { or } \mathrm{Na}^{+} \mathrm{Cl}^{-}$$
Similarly, the formation of $\mathrm{CaF}_2$ may be shown as
$$\underset{[A r] 4 \mathrm{~s}^2}{\mathrm{Ca}} \longrightarrow \underset{[A r]}{\mathrm{Ca}^{2+}}+2 e^{-}$$
$$\underset{[\mathrm{He}] 2 s^2 2 p^5}{\mathrm{~F}}+\mathrm{e}^{-} \longrightarrow \underset{[\mathrm{He}] 2 s^2 2 p^6 \text { or }[\mathrm{Ne}]}{\mathrm{F}^{-}}$$
$$\mathrm{Ca}^{2+}+2 \mathrm{~F}^{-} \longrightarrow \mathrm{CaF}_2 \text { or } \mathrm{Ca}^{2+}\left(\mathrm{F}^{-}\right)_2$$
Covalent bond The bond formed between the two atoms by mutual sharing of electrons between them is called covalent bond. e.g., the formation of chlorine molecule can be explained as
Similarly, in the formation of HCl
Arrange the following bonds in order of increasing ionic character giving reason.
$$\mathrm{N}-\mathrm{H}, \quad \mathrm{F}-\mathrm{H}, \quad \mathrm{C}-\mathrm{H} \text { and } \mathrm{O}-\mathrm{H}$$
Greater is the electronegativity difference between the two bonded atoms, greater is the ionic character.
| Bond | $$\mathrm{N-H}$$ | $$\mathrm{F-H}$$ | $$\mathrm{C-H}$$ | $$\mathrm{O-H}$$ |
|---|---|---|---|---|
| Electronegativity difference | $$(3.0-2.1)=0.9$$ | $$(4.0-2.1)=1.9$$ | $$(2.5-2.1)=0.4$$ | $$(3.5-2.1)=1.4$$ |
Therefore, increasing order of ionic character of the given bonds is as follows
$$\mathrm{C}-\mathrm{H}<\mathrm{N}-\mathrm{H}<\mathrm{O}-\mathrm{H}<\mathrm{F}-\mathrm{H}$$
Explain why $\mathrm{CO}_3^{2-}$ ion cannot be represented by a single Lewis structure. How can it be best represented?
A single Lewis structure of $\mathrm{CO}_3^{2-}$ ion cannot explain all the properties of this ion. It can be represented as a resonance hybrid of the following structures
If, it were represented only by one structure, there should be two types of bonds, i.e., $\mathrm{C}=\mathrm{O}$ double bond and C — O single bonds but actually all bonds are found to be identical with same bond length and same bond strength.
Predict the hybridisation of each carbon in the molecule of organic compound given below. Also indicate the total number of sigma and pi-bonds in this molecule.
The hybridisation and type of bonds of each carbon in the molecule given below
Group the following as linear and non-linear molecules.
$$\mathrm{H}_2 \mathrm{O}, \mathrm{HOCl}, \mathrm{BeCl}_2, \mathrm{Cl}_2 \mathrm{O}$$
The structure of the given molecules are
Therefore, only BeCl$$_2$$ is linear and rest of the molecules are non-linear.