Q67P - Chemistry: Molecular Nature Of Matter And Change

Question

Rank the members of each set of compounds in order of increasing the ionic character of their bonds. Use polar arrows to indicate the bond polarity of each:

(a) HBr, HCl, HI

(b) H₂O, CH₄ , HF

(c) SCI₂ , PCI₃ , SiCI₄ 

Step-by-Step Solution

Answer

The intermolecular force between the molecules are:

1. HBr, HCl, HI: The ionic character decreases as the electronegativity decreases down the group in the halogen series. So, the order of the ionic character is: HI < HBr < HCl.
2. H₂O , CH₄ , HF: The order of the ionic character is: CH₄ < H₂O <HF
3. SCI₂ , PCI₃ , SiCI₄ : The order of the ionic character is: SiCI₄ < SCI₂ < PCI₃.

Step 1: Intermolecular Forces

Intermolecular forces are the interaction which are formed by the attraction of the two having opposite charges (partial positive and partial negative charge). The opposite charge are formed by the presence of the electron-negative atom in the molecule. Due to the presence of an electron-negative atom, there is an induced partial positive charge is generated on the electron-positive charge (or less electron-negative charge) atom. There will be an attraction between the both oppositely charges to form a bond.

 

Dipole-dipole Interaction: These interactions are the attractive forces which present in the polar molecules. Polar molecules have permanent dipoles which are produced by the presence of the opposite charge of the atom. 

 

Ion-dipole interaction: These interactions are present in the ion and polar molecules. These interactions are similar to the dipole-dipole interaction.

 

London dispersion interaction: It is the weak bond which is formed for the short period of time. The bond is formed between the polar and non-polar molecules due to the phenomena of induction.

Step 2: Explanation

HBr, HCl, HI: In this molecule opens are involved with the electropositive H-atom. As we know, halogens are the most electronegative atom which tends to form a polar molecule and form an ionic bond. So, the order of the ionic character is: HI < HBr < HCl.

H₂O , CH₄ , HF: In H₂O molecule, there is the formation of the polar molecule due to the presence of electronegative O-atom with electropositive H-atom. In CH₄ , there are fewer electronegative atoms as their difference in electronegativity is less and hence forms a non-polar molecule with dispersion force. In HF, F-atom is the most electronegative atom forming a bond with the electropositive H-atom forming a polar bond. The order of the ionic character is:  CH₄ < H₂O < HF

SCI₂ , PCI₃, SiCI₄ : In SCI₂ molecule, There are electronegative Cl-atom belongs to halogen group form bond with S-atom forming dipole-dipole interaction. In PCI₃ , Cl-atom bonding with metal electropositive atom forming  with dipole-dipole interaction. In SiCI₄ , electronegative Cl-atom bonded with less electronegative S-atom forming dipole-dipole interaction. Therefore, the order of the ionic character is: SiCI₄ < SCI₂ < PCI₃ .