Question

For each of the bonds listed below, tell which atom is the more negatively charged. (a) \(\mathrm{C}-\mathrm{N}\) (b) \(\mathrm{C}-\mathrm{H}\) (c) \(\mathrm{C}-\mathrm{Br}\) (d) \(\mathrm{S}-\mathrm{O}\)

Short answer

(a) N, (b) C, (c) Br, (d) O

Step-by-step solution

Understand Electronegativity

Electronegativity is the tendency of an atom to attract electrons in a bond. The atom with higher electronegativity in a bond will be more negatively charged because it attracts the shared electrons more strongly.

Compare Electronegativity in C-N Bond

Carbon (C) has an electronegativity of 2.55, while Nitrogen (N) has an electronegativity of 3.04. Since nitrogen is more electronegative than carbon, it will be more negatively charged.

Compare Electronegativity in C-H Bond

Carbon (C) has an electronegativity of 2.55, and Hydrogen (H) has an electronegativity of 2.20. Carbon is more electronegative than hydrogen, thus carbon will be more negatively charged.

Compare Electronegativity in C-Br Bond

Carbon (C) has an electronegativity of 2.55, whereas Bromine (Br) has an electronegativity of 2.96. Bromine is more electronegative than carbon, so bromine will be more negatively charged.

Compare Electronegativity in S-O Bond

Sulfur (S) has an electronegativity of 2.58, and Oxygen (O) has an electronegativity of 3.44. Since oxygen is more electronegative than sulfur, oxygen will be more negatively charged.

Key concepts

Atomic Bonds

Atomic bonds are the connections formed between atoms to create molecules. Atoms seek stability, which is often achieved by having a full set of electrons in their outer shell. There are different types of atomic bonds, but a key characteristic of most bonds is the sharing or transfer of electrons between atoms.

• Covalent bonds: In covalent bonds, atoms share electron pairs, leading to the formation of molecules. These bonds can be single, double, or triple depending on the number of shared electron pairs.
• Ionic bonds: Here, atoms transfer electrons rather than share them. This transfer creates ions: one atom becomes positively charged, and the other becomes negatively charged, attracting each other.

The type of bond affects properties like conductivity, boiling and melting points, and solubility. Understanding atomic bonds is crucial for predicting the behavior and properties of different substances.

Chemical Polarity

Chemical polarity refers to the distribution of electric charge around atoms, molecules, or chemical groups. When atoms form bonds, the difference in electronegativity or ability to attract electrons can lead to polarity.
In a polar bond, one end is slightly negatively charged, while the other is slightly positively charged. This happens because the more electronegative atom pulls the shared electrons closer to itself, resulting in an uneven distribution of charges.

• Polar molecules: These are molecules with an uneven distribution of charge, leading to a net dipole moment. Water is a perfect example because the oxygen atom pulls the shared electrons more than the hydrogen atoms.
• Non-polar molecules: Molecules with symmetrically shared electron pairs have no net dipole moment. They tend to be symmetrical like \text{\(CO_2\)}, where oxygen pulls equally, canceling out any dipole.

Chemical polarity has significant effects on chemical properties and reactions, including solubility in differing solvents and interactions with other polar or non-polar substances.

Electron Sharing

Electron sharing is a fundamental concept in chemistry, especially when it comes to the formation of covalent bonds. In these bonds, two atoms share electron pairs to achieve stability. The shared electrons count towards each atom's outer electron shell, helping them achieve a full valence shell, akin to noble gases.
The sharing can be equal or unequal, depending on the electronegativities of the bonded atoms.

• Equal sharing: This occurs when two atoms have similar electronegativities. An example is \text{\(H_2\)}, where both hydrogen atoms equally share the electron pair because they have similar electronegativities.
• Unequal sharing: If one atom is more electronegative than the other, it pulls the shared electrons closer, resulting in a polarized bond. This unequal sharing is evident in molecules like water \text{\(H_2O\)}, where oxygen has a higher electronegativity compared to hydrogen, leading to a polar covalent bond.

Through these interactions, atoms achieve the stable electron configuration, driving the numerous chemical reactions and interactions around us.