Question

Determine whether each of the following molecules is polar: a. NO b. HF c. \(\mathrm{H}_{2}\) d. ICl

Short answer

NO and HF are polar molecules, while \(H_2\) is nonpolar. ICl is also polar due to a difference in electronegativity between I and Cl.

Step-by-step solution

Determine Polarity of NO

Look at the electronegativity difference between nitrogen (N) and oxygen (O). Since O is more electronegative than N, the electrons will be pulled closer to O, creating a dipole moment. NO is a diatomic molecule with a difference in electronegativity, therefore it is polar.

Determine Polarity of HF

Analyze the electronegativity difference between hydrogen (H) and fluorine (F). F is significantly more electronegative than H, creating a strong dipole moment in the molecule. As a result, HF is polar.

Determine Polarity of \(H_2\)

Look at the molecular structure of hydrogen (H2). This molecule consists of two identical atoms, so there is no difference in electronegativity and no dipole moment can be established. Hence, \(H_2\) is nonpolar.

Determine Polarity of ICl

Examine the electronegativity difference between iodine (I) and chlorine (Cl). Cl is more electronegative than I; this difference in electronegativity means that electrons will be pulled more towards Cl, leading to a dipole moment. Thus, ICl is polar.

Key concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that refers to an atom's ability to attract and hold onto electrons. It's a crucial factor in determining molecular polarity. Atoms with high electronegativity, such as fluorine (F), oxygen (O), and nitrogen (N), have a stronger pull on shared electrons in a chemical bond.

When different atoms form a bond, the one with higher electronegativity will attract the shared electrons more, creating an uneven electron distribution. This imbalance can lead to the formation of a dipole moment, where one end of the molecule becomes slightly negative and the other slightly positive. For example, in molecule pairs such as HF and NO, the significant difference in electronegativity between atoms leads to polarity in these molecules.

Dipole Moment

The dipole moment is a measure of the separation of positive and negative charges in a molecule. It's an important concept that helps us understand the nature of chemical bonds in polar molecules. A dipole is created when there is a difference in electronegativity between bonded atoms, resulting in an uneven charge distribution.

This separation of charges can be quantified as a vector, with a magnitude representing the strength of the polarity and a direction pointing from the positive to the negative pole. The larger the difference in electronegativity and the greater the distance between the atoms, the larger the dipole moment. Molecules like HF, with a high electronegativity difference, have strong dipole moments and are therefore very polar.

Polar Molecules

Polar molecules have an asymmetric distribution of electron density, leading to positive and negative poles within the molecule. This occurs because the atoms in these molecules have varying electronegativities, causing some atoms to pull electrons more towards themselves than others.

Polar molecules like HF and ICl exhibit a dipole moment where one end of the molecule has a slight negative charge while the other has a slight positive charge. This creates an electric field and enables the molecule to engage in dipole-dipole interactions with other polar molecules or ions, which significantly influences the physical properties, like solubility and boiling points.

Nonpolar Molecules

Nonpolar molecules, on the other hand, have symmetrical electron distributions resulting in no permanent dipole moment. These molecules typically consist of atoms with equal or very similar electronegativities, or their molecular shapes are arranged such that the individual dipole moments cancel each other out.

A clear example is the hydrogen molecule (H_2), where both hydrogen atoms have the same electronegativity, effectively sharing the electrons equally and generating no charge difference across the molecule. Nonpolar molecules do not mix well with polar molecules, like oil and water, and will usually exhibit weak intermolecular forces known as London dispersion forces.