Intramolecular Forces: Forces between atoms within a molecule (ionic or covalent bonds).
Ionic Bond: Formed when one atom loses an electron to another atom that gains it.
Covalent Bond: Formed by the sharing of electrons between atoms.
Factors Influencing Potential Energy
Covalent Molecules (e.g., H2)
Attraction between electrons and protons within atoms and between different atoms.
Potential Energy vs. Internuclear Distance:
Far apart atoms: Potential energy is zero.
Closer proximity: Attraction leads to decrease in potential energy.
Minimum potential energy at 74 pm internuclear distance.
Further closeness: Repulsion causes increase in potential energy.
Bond Length and Bond Energy
Bond Length: Distance between nuclei where potential energy is minimized.
Bond Energy/Enthalpy: Energy required to break one mole of bonds.
Increases with bond multiplicity (single, double, triple bonds).
Affected by the size of atoms and nature of bonds.
Factors Affecting Bond Length
Size of Atoms: Larger atoms lead to longer bond lengths.
Example: HF < HCl < HBr (increasing bond length with larger halogens).
Multiplicity of Bonds: Higher multiplicity (triple > double > single) leads to shorter bond lengths due to increased electron sharing.
Bond Enthalpy
Energy to break bonds (endothermic process).
Increases with bond multiplicity.
Decreases as bond length increases (weaker bonds).
Ionic Compounds
Formed through electron transfer (e.g., NaCl).
Ionic Bond Length: Calculated by adding radii of ions.
Potential Energy in Ionic Bonds:
Zero at large separation.
Minimum at certain distances due to attraction.
Increases with further closeness due to repulsion.
Lattice Enthalpy
Factors Affecting Lattice Enthalpy:
Size of Ions: Larger ions weaken attraction, reducing lattice enthalpy.
Charge of Ions: Higher charge increases attraction, enhancing lattice enthalpy.
Example: Magnesium oxide has higher lattice enthalpy than sodium chloride due to higher charge and smaller ion size.
Summary
Interaction strength between atoms affects potential energy and is influenced by factors like atom size and bond multiplicity for covalent bonds, and ion size and charge for ionic bonds. The relationship between potential energy and distance is crucial for understanding molecular stability and bond strength.