Problem 118 - Chemistry Matter and Change

Question

For each of the bonds listed, tell which atom is more negatively charged. \(\begin{array}{ll}{\text { a. } C-H} & {\text { c. } C-S} \\ {\text { b. } C-N} & {\text { d. } C-O}\end{array}\)

Step-by-Step Solution

Answer

a. C-H: Carbon b. C-N: Nitrogen c. C-S: Sulfur d. C-O: Oxygen

Step 1: (Step 1: Find Electronegativities of Atoms)

Look up the electronegativity values of each atom involved. In this case, we need the electronegativities of carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and sulfur (S). You can find these values in a periodic table or reference book: Electronegativities: Carbon (C) = 2.55 Hydrogen (H) = 2.20 Nitrogen (N) = 3.04 Oxygen (O) = 3.44 Sulfur (S) = 2.58

Step 2: (Step 2: Determine More Negatively Charged Atoms)

Using the electronegativity differences, compare the atoms in each bond to determine which one is more negatively charged: a. C-H Carbon (2.55) vs. Hydrogen (2.20) Difference: 0.35 More negatively charged atom: Carbon (C) b. C-N Carbon (2.55) vs. Nitrogen (3.04) Difference: 0.49 More negatively charged atom: Nitrogen (N) c. C-S Carbon (2.55) vs. Sulfur (2.58) Difference: 0.03 More negatively charged atom: Sulfur (S) d. C-O Carbon (2.55) vs. Oxygen (3.44) Difference: 0.89 More negatively charged atom: Oxygen (O)

Step 3: (Step 3: Write the Final Answer)

Now we can list the more negatively charged atom for each bond: a. C-H: Carbon b. C-N: Nitrogen c. C-S: Sulfur d. C-O: Oxygen

Key Concepts

Chemical Bonding

Understanding chemical bonding is crucial for anyone studying chemistry. Chemical bonds form when two atoms share or transfer electrons, leading to the formation of molecules and compounds. The nature of the bond depends on how equally electrons are shared between atoms. When electrons are shared equally, we have a nonpolar covalent bond; otherwise, it results in a polar covalent bond, with one atom having a slight negative charge and the other a slight positive charge.

In the case of ionic bonding, electrons are transferred from one atom to another, leading to the formation of positively charged cations and negatively charged anions. Electronegativity, the ability of an atom to attract electrons in a bond, plays a pivotal role in determining the bond type. The greater the difference in electronegativity between two bonded atoms, the more polarized the bond becomes. For instance, in the bonds C-H, C-N, C-S, and C-O, you would observe varying degrees of polarity due to differences in electronegativity, leading to one atom being more negatively charged than the other in each bond.

Periodic Table

The periodic table is more than just a tabular display of chemical elements; it is a powerful tool that provides a wealth of information about atomic properties. Elements in the periodic table are arranged in order of increasing atomic number, and are organized into periods (rows) and groups (columns) that display periodic trends. One of these trends is electronegativity, which generally increases from left to right across a period and decreases down a group.

When trying to determine which atom in a bond will be more negatively charged, the periodic table can guide us. For example, comparing electronegativity values, as in the given exercise (C-H, C-N, C-S, C-O), we can see the trend of increasing electronegativity moving from carbon to oxygen across period 2 of the periodic table. This trend helps us predict which atom will pull electrons closer to itself and hence bear a partial negative charge.

Atomic Properties

Atomic properties such as electronegativity, atomic radius, ionization energy, and electron affinity are essential to understanding chemical reactivity and bonding patterns. Electronegativity, in particular, is a key atomic property that influences how atoms bond. It describes the tendency of an atom to attract a shared pair of electrons when forming chemical bonds.

Smaller atoms with a large number of protons typically exhibit higher electronegativity because they can attract electrons more effectively. In our exercise, the atoms carbon, hydrogen, nitrogen, oxygen, and sulfur have different electronegativities, indicating their ability to attract electrons when bonded to carbon. Nitrogen, being smaller and with more protons than carbon, is more electronegative and therefore more likely to attract electrons, resulting in a partial negative charge on the nitrogen atom in the C-N bond, and similar reasoning applies to the other bonds discussed.