(a) 2 Por qué aumenta la intensidad de las fuerzas de...

(a) 2 Por qué aumenta la intensidad de las fuerzas de dispersión al aumentar la polarizabilidad? (b) Explique el aumento constante en el punto de ebullición de los gases nobles al aumentar el peso atómico (Tabla 11.3). (c) ¿Qué regla práctica obedece la relación entre fuerzas de dispersión y peso molecular? (d) Comente lo correcto o incorrecto de esta afirmación: "Si todos los demás factores son iguales, las fuerzas de dispersión entre las moléculas aumentan al incrementarse el número de electrones en las moléculas."

Key Concepts

Boiling Point Trends

The boiling point of a substance is influenced by the strength of its intermolecular forces. As dispersion forces become stronger with increasing molecular weight and polarizability, more energy is required to separate the molecules, leading to a higher boiling point. This trend is especially evident in nonpolar substances where dispersion forces dominate.

Molecular Weight and Electron Count

Molecular weight is often related to the number of electrons in a molecule, and an increase in the number of electrons typically results in a more polarizable electron cloud. Consequently, for molecules of similar structure, a higher molecular weight usually leads to stronger dispersion forces due to the increased electron count, which enhances polarizability.

Polarizability

This refers to the ease with which the electron cloud surrounding an atom or molecule can be distorted by an external electric field. Higher polarizability means a more easily distorted electron cloud, enhancing the ability to form temporary dipoles and thus increasing the strength of dispersion forces.

London Dispersion Forces

These are weak intermolecular forces that arise due to temporary fluctuations in electron distribution within molecules, leading to the formation of instantaneous dipoles that induce further dipoles in neighboring molecules. They are present in all substances but are the only type of intermolecular force acting in nonpolar compounds.

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