Question

Order the following elements from lowest electronegativity to highest: \(\mathrm{P}, \mathrm{C}, \mathrm{N}, \mathrm{H}, \mathrm{O}, \mathrm{S}\). Use your ordering of the atoms to rank the following hydrogen bonds from weakest to strongest: a. \(\mathrm{SH}-\mathrm{O}\) b. \(\mathrm{NH}-\mathrm{O}\) c. \(\mathrm{OH}-\mathrm{O}\)

Short answer

Electronegativity order: \( \text{P < S < H < C < N < O} \). Hydrogen bond strength: \( \text{SH-O < NH-O < OH-O} \).

Step-by-step solution

Recall Electronegativity Trends

Electronegativity increases as you move from left to right across a period and decreases as you move down a group in the periodic table. This means elements in the same period will have increasing electronegativity from left to right, and elements in the same group will have decreasing electronegativity as you go down.

Determine Relative Electronegativity

Locate each element: Phosphorus (P), Carbon (C), Nitrogen (N), Hydrogen (H), Oxygen (O), and Sulfur (S). In the periodic table, these elements can be ordered based on above trend: - Hydrogen is less electronegative than Carbon. - Carbon is less electronegative than Nitrogen. - Nitrogen is less electronegative than Oxygen. - Phosphorus is less electronegative than Sulfur because Phosphorus is above Sulfur in the periodic table.

Order Elements by Electronegativity

Using the periodic table and general electronegativity values, we order the elements as: \[ \text{P < S < H < C < N < O} \] This indicates Phosphorus has the lowest electronegativity and Oxygen has the highest.

Understand Hydrogen Bond Strength

The strength of a hydrogen bond depends on the electronegativity of the elements involved. More electronegative atoms form stronger hydrogen bonds with hydrogen because they can pull the hydrogen closer.

Rank Hydrogen Bonds

Based on the order of electronegativity:- In \( \text{SH-O} \), Sulfur is bonding with Oxygen.- In \( \text{NH-O} \), Nitrogen is bonding with Oxygen.- In \( \text{OH-O} \), Oxygen is bonding with Oxygen. Thus, the hydrogen bonds are ranked as: \[ \text{SH-O (weakest) < NH-O < OH-O (strongest)} \]

Key concepts

Periodic Table Trends

Electronegativity is a key concept in understanding how atoms interact in chemical reactions. It is the tendency of an atom to attract electrons towards itself. The periodic table showcases a distinct trend in electronegativity across periods and groups.

• Across a Period: As you move from left to right across a period, electronegativity values increase. This is because the number of protons in the nucleus increases, pulling electrons more strongly towards the atom.
• Down a Group: Electronegativity decreases as you move down a group. Although the number of protons increases, the additional electron shells reduce the effective nuclear charge experienced by outer electrons.

Understanding these trends helps in predicting how different elements will behave in chemical bonding situations. For instance, in our exercise, we determined that oxygen, being the most electronegative, would have the strongest pull on electrons among the provided elements.

Hydrogen Bonding

Hydrogen bonding is a special type of dipole-dipole interaction that occurs when hydrogen is covalently bonded to a highly electronegative atom, such as oxygen or nitrogen. This creates a scenario where the hydrogen atom acquires a positive partial charge, which can interact with other negative charges nearby. A few points to note about hydrogen bonding:

• Hydrogen bonds are stronger than van der Waals forces but weaker than covalent and ionic bonds.
• The strength of a hydrogen bond increases with the increasing electronegativity of the atom hydrogen is bonded to.
• Hydrogen bonds play a critical role in biological structures, such as the stability of DNA and proteins.

In the exercise, the concept of hydrogen bonding was used to rank the strengths of bonds like SH-O, NH-O, and OH-O. Due to oxygen's high electronegativity, OH-O forms the strongest hydrogen bond, while SH-O is the weakest.

Chemical Bond Strength

Chemical bonds vary in strength, and understanding their relative strength is essential for predicting chemical behavior and reactivity. Generally, bond strength is determined by the bond's length, energy, and atom types involved.

• Stronger bonds are typically shorter and require more energy to break.
• Covalent bonds are usually stronger than intermolecular forces like hydrogen bonds or van der Waals forces.
• The difference in electronegativity between atoms contributes significantly to bond strength; the greater the difference, the stronger the bond.

In the context of our exercise, since hydrogen bonds vary in strength based on electronegativity, OH-O represents the strongest bond due to oxygen-oxygen interaction which maximizes electron density sharing. The insights into bond strength help in areas such as molecular biology and materials science, where controlling interactions is crucial.