Question

Describe the type of bonding that exists in the \(\mathrm{Cl}_{2}(g)\) molecule. How does this type of bonding differ from that found in the \(\mathrm{HCl}(g)\) molecule? How is it similar?

Short answer

In a Cl\(_2\) molecule, the bonding is nonpolar covalent due to equal sharing of electrons between two identical chlorine atoms. In contrast, an HCl molecule has a polar covalent bond as the electrons are more attracted to the more electronegative chlorine atom, resulting in a dipole moment. However, the bonds in both Cl\(_2\) and HCl are covalent, with the molecules consisting of two atoms held together by a single covalent bond.

Step-by-step solution

Identify the type of bond in Cl\(_2\) molecule

In a Cl\(_2\) molecule, there are two chlorine atoms sharing a pair of electrons. Since both atoms are the same element and have the same electronegativity, the electron pair is shared equally between the two atoms. This type of bond is called a nonpolar covalent bond.

Identify the type of bond in HCl molecule

In an HCl molecule, there is a hydrogen atom and a chlorine atom. The electronegativity of these two atoms is different, with chlorine being more electronegative than hydrogen. As a result, the shared electrons are more attracted to the chlorine atom, creating a polar covalent bond. This means that there is a slightly positive charge on the hydrogen atom and a slightly negative charge on the chlorine atom, giving the molecule a dipole moment (a measure of the separation of positive and negative charges in a molecule).

Analyze differences between Cl\(_2\) and HCl bonds

Here are the main differences between the bonding in Cl\(_2\) and HCl molecules: 1. Cl\(_2\) has a nonpolar covalent bond, while HCl has a polar covalent bond. 2. In Cl\(_2\), the electrons are shared equally between the two chlorine atoms, while in HCl, the electrons are more attracted to the chlorine atom than the hydrogen atom, due to the electronegativity difference. 3. Due to the polar nature of the HCl bond, the molecule has a dipole moment, while Cl\(_2\) molecule has no dipole moment because of its nonpolar bond.

Analyze similarities between Cl\(_2\) and HCl bonds

Despite their differences, both Cl\(_2\) and HCl have some similarities in their bonding: 1. Both bonds are covalent, meaning that the atoms involved share electrons rather than transferring them completely (like in an ionic bond). 2. Both molecules consist of two atoms that are held together by a single covalent bond.

Key concepts

Nonpolar Covalent Bonds

Nonpolar covalent bonds occur when two atoms share a pair of electrons equally. This happens because the atoms involved have the same or very similar electronegativity, which is the tendency of an atom to attract electrons. In a molecule like \( ext{Cl}_2\), both chlorine atoms pull the electrons with the same strength. Therefore, the electrons remain in the middle, creating a nonpolar covalent bond.

Key characteristics of nonpolar covalent bonds include:

• The shared electrons spend equal time around each nucleus.
• The molecule usually does not have charged ends (dipoles).
• Found in diatomic molecules like \( ext{O}_2\), \( ext{N}_2\), and \( ext{Cl}_2\).

Overall, the lack of electronegativity difference makes these bonds stable and even, with no partial charges on either end of the molecule.

Polar Covalent Bonds

Unlike nonpolar covalent bonds, polar covalent bonds involve an unequal sharing of electrons due to different electronegativities. When two atoms of different electronegativities form a bond, like in \(HCl\), the shared electrons are pulled more towards the more electronegative atom - in this case, chlorine.

This results in a molecule that has a partial negative charge near the chlorine and a partial positive charge near the hydrogen, forming a dipole. Here's what you should remember:

• One end of the bond is slightly negative, and the other is slightly positive.
• These differences create a dipole moment, a vector quantity showing charge distribution.
• Polar covalent bonds are common in molecules like water (\(H_2O\)) and ammonia (\(NH_3\)).

Such bonds give these molecules unique properties, like the ability to dissolve in water, due to their polar nature.

Electronegativity

Electronegativity is a measure of how strongly an atom attracts bonding electrons. It's a key factor in determining the type of bond that will form between two atoms.

In the periodic table, electronegativity generally increases across a period and decreases down a group. This means:

• Fluorine is the most electronegative element, while elements like francium and cesium have very low electronegativity.
• A large difference in electronegativity (> 2.0) usually leads to ionic bonds, while a smaller difference leads to polar covalent bonds.
• Very small or no difference at all leads to nonpolar covalent bonds.

Understanding electronegativity helps predict whether a molecule will be polar or nonpolar based on the atoms involved.

Dipole Moment

A dipole moment measures the separation of charge within a molecule due to uneven electron sharing. In molecules with polar covalent bonds, such as \(HCl\), a dipole moment exists because one atom pulls electrons more strongly, causing partial charges.

Why is this important?

• It indicates a molecule's polarity and helps predict its behavior in electric fields.
• The greater the electronegativity difference, the larger the dipole moment.
• Molecules with no dipole moment are usually nonpolar, while those with a dipole moment are polar.

Dipole moments can also affect intermolecular forces and influence boiling and melting points, solubility, and other physical properties of substances.