The key difference between hydrogen bond and ionic bond is that ionic bonding exists between permanent anions and cations, whereas hydrogen bonds exist between partial positive and partial negative charges.
Chemical bonds hold atoms and molecules together. Bonds are important in determining the chemical and physical behaviour of molecules and atoms. As proposed by the American chemist G.N.Lewis, atoms are stable when they contain eight electrons in their valence shell. Most atoms have less than eight electrons in their valence shells (except the noble gases in the group 18 of the periodic table); therefore, they are not stable. These atoms tend to react with each other to become stable. Thus, each atom can achieve a noble gas electronic configuration. Ionic bonds are one such chemical bond, which connects atoms in chemical compounds. Hydrogen bonds are intermolecular attractions between molecules.
CONTENTS
1. Overview and Key Difference
2. What is Hydrogen Bond
3. What is Ionic Bond
4. Side by Side Comparison – Hydrogen Bond vs Ionic Bond in Tabular Form
5. Summary
What is Hydrogen Bond?
When hydrogen is attached to an electronegative atom like fluorine, oxygen or nitrogen, it will create a polar bonding. Due to electronegativity, the electrons in the bond gets attracted to the electronegative atom more than to the hydrogen atom. Therefore, the hydrogen atom will get a partial positive charge, whereas the more electronegative atom will get a partial negative charge. When two molecules having this charge separation are close by, an attraction force rises between hydrogen and the negatively charged atom. We call this hydrogen bonding.
Hydrogen bonds are relatively stronger than other dipole interactions, and they determine the molecular behaviour. For example, water molecules have intermolecular hydrogen bonding. One water molecule can form four hydrogen bonds with another water molecule. Since oxygen has two lone pairs, it can form two hydrogen bonds with positively charged hydrogen. Then, we can call the two water molecules as a dimer. Each water molecule can bind with four other molecules because of the hydrogen bonding capability. It result in a higher boiling point for water, even though a water molecule has a low molecular weight. Therefore, the energy needed to break the hydrogen bonds when they are going to the gaseous phase is high.
Figure 01: Hydrogen Bonds Between Water Molecules
Furthermore, hydrogen bonds determine the crystal structure of ice. The unique arrangement of ice lattice helps it to float on water; hence, protecting the aquatic life in the winter period. Other than this, hydrogen bonding plays a vital role in biological systems. The three-dimensional structure of proteins and DNA are solely based on hydrogen bonds. Moreover, hydrogen bonds can be destroyed by heating and mechanical forces.
What is Ionic Bond?
Atoms can gain or lose electrons and form negative or positive charged particles, respectively. These particles are called ions. There are electrostatic interactions between the ions. Ionic bonding is the attractive force between these oppositely charged ions. The strength of the electrostatic interactions is largely influenced by the electronegativity values of the atoms in an ionic bond. Electronegativity gives a measurement of the atoms’ affinity for electrons. An atom with high electronegativity can attract electrons from an atom with low electronegativity to form an ionic bond.
Figure 02: Formation of Ionic Bond in Sodium Chloride
For example, sodium chloride has an ionic bond between sodium ion and chloride ion. Sodium is a metal; therefore, it has a very low electronegativity (0.9) compared to Chlorine (3.0). Because of this electronegativity difference, Chlorine can attract an electron from Sodium and form Cl- and Na+ ions. Because of this, both atoms gain the stable, noble gas electronic configuration. Cl- and Na+ are held together by very strong attractive electrostatic forces, thus forming an ionic bond.
What is the Difference Between Hydrogen Bond and Ionic Bond?
Hydrogen bonds are intermolecular attractions while ionic bonds are attractive electrostatic forces. The key difference between hydrogen bond and ionic bond is that ionic bonding exists between permanent anions and cations, whereas hydrogen bonds exist between partial positive and partial negative charges. Additionally, ionic bonds are stronger than hydrogen bonds.
Moreover, hydrogen bonds occur when there is a hydrogen atom and an electronegative atom while ionic bonds occur between any metal and nonmetal atom. So, this is a significant difference between hydrogen bond and ionic bond. Besides, a further difference between hydrogen bond and ionic bond is that the hydrogen bonds are easy to break because they are either intermolecular or intramolecular attraction forces, but ionic bonds are strong chemical bonds which are difficult to break.
Summary – Hydrogen Bond and Ionic Bond
Ionic bonds occur within ionic compounds. Hydrogen bonds are inter-molecular bonds. The key difference between hydrogen bond and ionic bond is that ionic bonding exists between permanent anions and cations, whereas hydrogen bonds exist between partial positive and partial negative charges.