Hydrogen Bond vs Ionic Bond
Chemical bonds hold atoms and molecules together. Bonds are important in determining the chemical and physical behavior 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 of the 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 bond is one such chemical bond, which connects atoms in chemical compounds. Hydrogen bonds are intermolecular attractions between molecules.
When hydrogen is attached to an electronegative atom like fluorine, oxygen or nitrogen, a polar bonding will result. Because of the electronegativity, the electrons in the bond will be more attracted to the electronegative atom than to the hydrogen atom. Therefore, 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, there will be an attraction force between hydrogen and the negatively charged atom. This attraction is known as hydrogen bonding.
Hydrogen bonds are relatively stronger than other dipole interactions, and they determine the molecular behavior. 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 the two water molecules can be known as a dimer. Each water molecule can bond with four other molecules because of the hydrogen bonding capability. This result in a higher boiling point for water, even though a water molecule has a low molecular weight. Therefore, energy needed to break the hydrogen bonds when they are going to the gaseous phase is high. Further, hydrogen bonds determine the crystal structure of ice. The unique arrangement of ice lattice helps it to float on water, hence protects 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. Hydrogen bonds can be destroyed by heating and mechanical forces.
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 electronegativities 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. 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 attractive electrostatic forces, thus forming an ionic bond.
What is the difference between Hydrogen Bond and Ionic Bond?
• Ionic bonds are resulted within ionic compounds. Hydrogen bonds are inter-molecular bonds.
• Ionic bonds are stronger than hydrogen bonds.
• To have a hydrogen bond, hydrogen atom should be there. Ionic bonds can be occurred between any metal and non metal atom.
• Ionic bonding exists between permanent anions and cations whereas hydrogen bonds exist between partial positive and partial negative charges.