Which substance would have the point weakest intermolecular forces of attraction? CHA NaCl H2O MgF2
The Correct Answer and Explanation is:
Correct Answer: CH₄
Intermolecular forces (IMFs) are the attractive or repulsive forces that exist between neighboring chemical entities, such as atoms, molecules, or ions. The strength of these forces dictates a substance’s physical properties, including its melting point, boiling point, and state of matter at a given temperature. To determine which substance has the weakest forces, one must identify the primary type of force present in each compound.
The substances can be categorized based on their bonding and molecular structure:
- NaCl (Sodium Chloride) and MgF₂ (Magnesium Fluoride): These are ionic compounds, formed between a metal and a nonmetal. They do not exist as discrete molecules but as extensive three-dimensional crystal lattices. The particles (Na⁺ and Cl⁻ ions in NaCl; Mg²⁺ and F⁻ ions in MgF₂) are held together by extremely strong electrostatic attractions known as ionic bonds. These forces are significantly stronger than any of the forces found between neutral molecules.
- H₂O (Water): Water is a polar molecular compound. The oxygen atom is highly electronegative, creating a significant partial negative charge, while the hydrogen atoms carry partial positive charges. Due to the presence of hydrogen atoms bonded directly to a highly electronegative oxygen atom, water molecules exhibit hydrogen bonding. Hydrogen bonds are the strongest type of intermolecular force, resulting in water’s unusually high boiling point for its small size.
- CH₄ (Methane): Methane is a nonpolar molecular compound. The electronegativity difference between carbon and hydrogen is very small, and its symmetrical tetrahedral geometry ensures that any minor bond polarity cancels out. As a nonpolar molecule, the only intermolecular forces methane can experience are London dispersion forces. These are the weakest type of IMF, arising from temporary, induced dipoles caused by the random movement of electrons.
In conclusion, the forces of attraction are ranked as follows: ionic bonds (in NaCl and MgF₂) > hydrogen bonding (in H₂O) > London dispersion forces (in CH₄). Therefore, methane (CH₄) has the weakest intermolecular forces of attraction.
