Which of the following substance has the highest melting point?
- BaO
- MgO
- KCI
- NaCI
The Correct Option is B
Approach Solution - 1
Approach Solution -2
Ans. Lattice energy is necessary for the melting point, thus we should presumably consider the optimal circumstances that lead to lattice energy in this situation. We want both the cation and anion to have a high charge density for the stronger ionic character, and ideally, the ions should be the least polarizable.
- The oxyanion is a more suitable option than the chloride anion.
- Since Mg2+ is smaller than Ba2+ and has a +2 charge, MgO will have the greatest melting point out of the compounds mentioned.
- This implies that the substance will also have the highest lattice energy.
- As part of the displacement process, the valence electrons for both magnesium and oxygen are transferred, creating the ionic compound magnesium oxide (MgO).
- Due to the strong covalent bond, the cation (Mg2+) and anion (O2-) in MgO subsequently form an ionic bond.
- The crystal lattice of magnesium oxide has an octahedral geometry, a halite-like form, and a lattice constant of "a=4.212Ao."
- A strong bond between the Mg2+ and O2- ions causes the material to have a high melting point.
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Concepts Used:
Chemical Bonding and Molecular Structure
Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.
Types of Chemical Bonds:
There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds.
- Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
- Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding.
- Hydrogen Bonds - It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
- Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.
Factors Affecting Bond Enthalpy in Chemical Bonding:
- Size of the Atom
- Multiplicity of Bonds
- Number of Lone Pair of Electrons Present
- Bond Angle