Question

In each of the following diatomic molecules, which end of the molecule is negative relative to the other end? a. hydrogen chloride, HCl b. carbon monoxide, \(\mathrm{CO}\) c. bromine monofluoride, BrF

Short answer

a. In HCl, the Cl end is more negative. b. In CO, the O end is more negative. c. In BrF, the F end is more negative.

Step-by-step solution

Find the electronegativity of each atom in the molecule

Use a periodic table or electronegativity table to look up the electronegativity values of each atom in the diatomic molecule. a. For hydrogen chloride, HCl: Electronegativity of hydrogen (H) = 2.20 Electronegativity of chlorine (Cl) = 3.16 b. For carbon monoxide, CO: Electronegativity of carbon (C) = 2.55 Electronegativity of oxygen (O) = 3.44 c. For bromine monofluoride, BrF: Electronegativity of bromine (Br) = 2.96 Electronegativity of fluorine (F) = 3.98

Identify the higher electronegativity values and their corresponding atoms

Compare the electronegativity values of the atoms in each molecule to identify the atom with the higher electronegativity value. a. For HCl, chlorine (Cl) has a higher electronegativity value than hydrogen (H). b. For CO, oxygen (O) has a higher electronegativity value than carbon (C). c. For BrF, fluorine (F) has a higher electronegativity value than bromine (Br).

Determine which end of the molecule is negative relative to the other end

Based on the higher electronegativity values and corresponding atoms identified in step 2, determine which end is negative relative to the other end. a. In HCl, the chlorine (Cl) end of the molecule is more negative due to its higher electronegativity value. b. In CO, the oxygen (O) end of the molecule is more negative due to its higher electronegativity value. c. In BrF, the fluorine (F) end of the molecule is more negative due to its higher electronegativity value.

Final Answer:

a. In hydrogen chloride, HCl, the chlorine (Cl) end is more negative relative to the hydrogen (H) end. b. In carbon monoxide, CO, the oxygen (O) end is more negative relative to the carbon (C) end. c. In bromine monofluoride, BrF, the fluorine (F) end is more negative relative to the bromine (Br) end.

Key concepts

Diatomic Molecules

Diatomic molecules are simply molecules composed of only two atoms. These could potentially be atoms of the same element, like oxygen ( O_2 ), or different elements, such as in carbon monoxide ( CO ). When these atoms are bonded together, they form a molecule.
Diatomic molecules exhibit different properties depending on the elements involved. For example:

• They can be either polar or non-polar depending on the electronegativity difference between the two atoms.
• In non-polar diatomic molecules, like nitrogen ( N_2 ), the electronegativity difference is virtually zero, so electrons are equally shared.
• In polar diatomic molecules, such as hydrogen chloride ( HCl ), the electrons are more attracted to one atom, making one side of the molecule slightly more negative.

Understanding these properties is crucial when discussing diatomic molecules and their behavior in various chemical reactions.

Chemical Polarity

Chemical polarity refers to the distribution of electrical charge around atoms, chemical groups, or molecules. In diatomic molecules, chemical polarity arises due to differences in electronegativity.
When one atom in a diatomic molecule is more electronegative than the other, it attracts shared electrons more strongly. This results in an uneven distribution of electron density, making the molecule polar:

• The atom with the higher electronegativity becomes partially negative, forming the negative pole.
• The less electronegative atom becomes partially positive, forming the positive pole.

For example, in hydrogen chloride ( HCl ), chlorine has a higher electronegativity than hydrogen, so the chlorine end of the molecule is more negative. Polarity is a crucial concept in chemistry because it affects how molecules interact with each other, influencing properties like solubility and reactivity.

Molecular Structure

The molecular structure of a compound is determined by the arrangement of its atoms and the type of chemical bonds between them. In simple diatomic molecules, this structure is straightforward as it involves just two atoms. The characteristics of these molecules are influenced primarily by the type of bond formed.
There are a few types of bonds that can occur:

• Covalent Bonds: These bonds involve the sharing of electron pairs between two atoms, often leading to the formation of diatomic molecules.
• Ionic Bonds: Not common in diatomic molecules since this type of bond usually occurs in compounds rather than between just two atoms, involving electron transfer rather than sharing.

The bond type, along with atom electronegativity, determines the molecule's shape and polarity. For instance, in molecules like carbon monoxide ( CO ), a triple covalent bond forms, and the dipole moment created by the difference in electronegativities gives the molecule its polarity.

Electronegativity Values

Electronegativity is the measure of an atom's ability to attract and hold onto electrons within a chemical bond. It's a crucial concept for predicting how atom pairs in diatomic molecules will interact and which part of the molecule will be more electronegative.
In the periodic table,

• Elements on the top right, like fluorine, tend to have higher electronegativity values.
• Elements on the bottom left, such as cesium, have lower electronegativity values.

These values are used to determine if a molecule is polar or non-polar. A larger difference in electronegativity between two bonded atoms indicates a higher polarity. In examples like bromine monofluoride ( BrF ), fluorine is much more electronegative than bromine, making the fluorine end of the molecule significantly more negative. By understanding electronegativity, chemists can predict molecular interactions and chemical behavior.