Question

Four atoms are arbitrarily labeled \(\mathrm{D}, \mathrm{E}, \mathrm{F},\) and \(\mathrm{G}\). Their electronegativities are as follows: \(\mathrm{D}=3.8, \mathrm{E}=3.3, \mathrm{~F}=\) \(2.8,\) and \(\mathrm{G}=1.3 .\) If the atoms of these elements form the molecules \(\mathrm{DE}, \mathrm{DG}, \mathrm{EG},\) and \(\mathrm{DF},\) how would you arrange these molecules in order of increasing covalent bond character?

Short answer

DE, DF, EG, DG

Step-by-step solution

Understand Electronegativity

Electronegativity is the tendency of an atom to attract a shared pair of electrons. When two atoms form a bond, the difference in their electronegativity values can indicate the bond's character. Larger differences mean more ionic character, while smaller differences mean more covalent character.

Calculate Electronegativity Differences

Calculate the electronegativity difference for each molecule:- For DE: \(|3.8 - 3.3| = 0.5\)- For DG: \(|3.8 - 1.3| = 2.5\)- For EG: \(|3.3 - 1.3| = 2.0\)- For DF: \(|3.8 - 2.8| = 1.0\)

Arrange by Electronegativity Difference

The molecules are ordered by increasing electronegativity difference, which correlates to increasing ionic character. Therefore, arrange the molecules by increasing covalent character, meaning those with smaller electronegativity differences are more covalent: - DE (0.5) - DF (1.0) - EG (2.0) - DG (2.5)

Final Arrangement

The final order of molecules, from increasing covalent to increasing ionic character, is: DG, EG, DF, DE. Since we want increasing covalent character, reverse this order: DE, DF, EG, DG.

Key concepts

Covalent Bond Character

When we talk about the covalent bond character in a molecule, we are discussing the nature of the sharing of electrons between the atoms involved. Covalent bonds are characterized by the sharing of electron pairs between atoms. The more evenly the electrons are shared, the greater the covalent character. In a perfect covalent bond, atoms share electrons equally. However, in reality, differences in electronegativity between atoms can cause an unequal sharing of electrons. This results in a polar covalent bond where one atom attracts the shared electrons more strongly than the other. Understanding covalent bond character is crucial for predicting molecular structure and properties:

• High covalent character indicates a strong, mostly equal sharing of electrons.
• Affected by the differences in electronegativity, with smaller differences suggesting stronger covalent nature.
• Influences properties such as polarity, solubility, and melting/boiling points of molecules.

Ionic Bond Character

Ionic bond character refers to the degree to which a bond between two atoms displays ionic properties. An ionic bond is formed when there is a complete transfer of one or more electrons from one atom to another, resulting in the formation of charged ions. The presence of ionic bond character in a bond points toward a higher difference in electronegativity between the two atoms:

• Large differences (>1.7 on the Pauling scale) in electronegativity result in ionic bonds.
• Ionic character leads to the formation of ions and results in high melting and boiling points due to the strong electrostatic forces of attraction.
• Ionic compounds tend to be soluble in polar solvents and conduct electricity when dissolved or in molten state.

Understanding ionic bond character helps in predicting the stability, reactivity, and solubility of compounds.

Electronegativity Differences

Electronegativity differences between atoms play a pivotal role in determining the type of bond that forms between them. The greater the difference, the more polarization occurs between the bonded atoms. To simply understand the concept:

• Small differences (0 to 0.4) usually result in nonpolar covalent bonds where electrons are shared equally.
• Moderate differences (0.4 to 1.7) result in polar covalent bonds, with unequal sharing of electrons.
• Large differences (>1.7) are indicative of ionic bonding where one atom donates electrons to another.

In our discussed exercise, calculating these differences helps in assessing each molecule's bond character. For example, in molecule DE with an electronegativity difference of 0.5, the bond is more covalent. Meanwhile, in DG, with a larger difference of 2.5, the bond leans towards being ionic.

Chemical Bonding

Chemical bonding refers to the attraction between atoms that allows the formation of chemical substances. Bonds can be broadly classified into covalent, ionic, and metallic bonds, based on electron sharing or transfer: - **Covalent bonds**: Involves the sharing of electron pairs between atoms. Strong stability and specific orientation lead to unique molecule properties. - **Ionic bonds**: Involves the complete transfer of electrons, forming cations and anions. These compounds form crystalline lattice structures that confer distinctive properties like high melting points. Chemical bonding determines how atoms are held together in molecules, affecting every aspect of a substance's physical and chemical properties. For students, grasping the fundamentals of chemical bonding is essential as it serves as a basis for understanding complex molecular interactions and reactions. Exploring these bonds allows us to explain why certain materials behave the way they do-and draws a line between merely knowing elements and understanding chemistry.