Problem 7 - Biology Concepts and Applications

Question

In a hydrogen bond, a covalently bound hydrogen atom weakly attracts an _____ in a different molecule or a different region of the same molecule. a. ion b. electronegative atom

Step-by-Step Solution

Answer

b. electronegative atom

Step 1: Identify Hydrogen Bonds

Hydrogen bonds occur when a hydrogen atom covalently bound to a more electronegative atom, such as nitrogen, oxygen, or fluorine, experiences an attraction to another electronegative atom. This is important because hydrogen bonds do not form with just any atom; they specifically involve electronegative atoms.

Step 2: Assess the Answer Choices

Consider the options given: (a) ion and (b) electronegative atom. Recall that hydrogen bonds typically involve electronegative atoms, not ions, which are generally charged particles.

Step 3: Choosing the Correct Answer

Based on the nature of hydrogen bonds, we can deduce that the correct choice is the option that involves electronegative atoms, because hydrogen forms weak attractions specifically with electronegative atoms.

Key Concepts

Electronegativity

Electronegativity is a chemical property that describes the tendency of an atom to attract electrons to itself. This concept is fundamental in understanding many chemical interactions, including the formation of bonds and molecular behavior.
This property varies across the periodic table, typically increasing from left to right, as atomic size decreases and the number of valence electrons increases.

• More electronegative atoms attract electrons more effectively.
• Elements like fluorine, oxygen, and nitrogen are highly electronegative.

These elements often participate in hydrogen bonding due to their strong pull on electron density. Electronegativity is crucial in explaining why hydrogen bonds tend to form with specific atoms.
A more electronegative atom will create a partial positive charge on the hydrogen atom, fostering an attraction to another electronegative atom in a different molecule or region, which is the essence of hydrogen bonding.

Covalent Bonds

Covalent bonds form when two atoms share one or more pairs of electrons. This sharing allows the atoms to attain a more stable electron arrangement.
Hydrogen bonds occur when a hydrogen atom involved in a covalent bond is also attracted to another electronegative atom, forming a weak connection that is vital in many biological and chemical systems.

• Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs.
• The bond strength and length can vary based on the involved atoms and the number of shared electron pairs.

These bonds are fundamentally different from hydrogen bonds, which are weaker and not true bonds.
However, the presence of a covalent bond is a prerequisite for hydrogen bonding, as the hydrogen must first be covalently bonded to a more electronegative atom.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion that occur between neighboring molecules. These forces are significantly weaker than the intramolecular forces (like covalent bonds) that hold a molecule together.
Hydrogen bonds are a type of intermolecular force and play a crucial role in determining the physical properties of substances.

• They are responsible for the unique properties of water, including its high boiling point and surface tension.
• These forces are also key in the structure and function of biological macromolecules like DNA and proteins.

Hydrogen bonds illustrate how intermolecular forces can significantly affect how molecules interact with each other.
These forces are based on the concept of electronegativity, as they often involve an electronegative atom that attracts a hydrogen atom from another molecule. Understanding intermolecular forces can give insights into molecular interactions, states of matter, and the behavior of substances under various conditions.