Problem 10 - Anatomy and Physiology of Animals

Question

A molecule of ammonia contains one atom of nitrogen and three atoms of hydrogen. These are linked with ________. a. ionic bonds b. nonpolar covalent bonds c. polar covalent bonds d. hydrogen bonds

Step-by-Step Solution

Answer

Ammonia contains polar covalent bonds.

Step 1: Understand the Molecule Composition

Ammonia (NH₃) consists of one nitrogen atom and three hydrogen atoms. To determine the type of bonds in the molecule, we first recognize that both elements are non-metals.

Step 2: Identify Bond Types for Non-metals

When atoms of non-metal elements bond, they usually form covalent bonds. This is because they tend to share electrons rather than transfer them as seen in ionic bonds.

Step 3: Determine Electronegativity Difference

We look at the electronegativity of nitrogen and hydrogen. Nitrogen has a higher electronegativity compared to hydrogen. An electronegativity difference exists when the values for the bonded atoms differ.

Step 4: Classify the Covalent Bond Type

Since there is an electronegativity difference between nitrogen and hydrogen, the shared electrons are not equally distributed. This uneven distribution of electrons indicates a polar covalent bond, as opposed to a nonpolar covalent bond, where electrons are shared equally.

Step 5: Finalize the Answer

Considering the described electronegativity difference and uneven sharing of electrons, ammonia's bonds are best described as polar covalent bonds.

Key Concepts

Polar Covalent Bonds

In chemistry, bonds between atoms can be classified based on how the electrons are shared between them. Polar covalent bonds are a type of covalent bond where the electrons shared by the atoms are unequally distributed. This occurs when the two atoms involved in the bond have different electronegativities, leading to a partial positive charge on one atom and a partial negative charge on the other.
This creates a dipole moment in the molecule, where one end of the bond is slightly more negative and the other slightly more positive.

• Electrons are not equally shared.
• Creates a molecule with a positive pole and a negative pole.
• Often found in molecules where atoms have different electronegativities.

Polar covalent bonds are essential to many properties of molecules, such as solubility and boiling points, as they influence how molecules interact with one another.

Ammonia Molecule

An ammonia molecule, with the chemical formula NH₃, is a classic example of a molecule with polar covalent bonds. It consists of one nitrogen atom bonded to three hydrogen atoms.
The structure of ammonia is trigonal pyramidal, with the nitrogen atom at the apex and the hydrogen atoms forming the three corners of a pyramid.
Due to the shape and the electronegativity differences between nitrogen and hydrogen, ammonia is polar.

• Nitrogen atom bonds with three hydrogen atoms.
• Overall molecular shape contributes to polarity.
• Used in industrial applications and agriculture.

Ammonia is widely used in fertilizers and cleaning products. Its ability to be a strong cleaning agent is partly due to its polar nature, which allows it to dissolve easily in water.

Electronegativity Difference

Electronegativity is a measure of how strongly atoms attract bonding electrons to themselves. When forming chemical bonds, particularly covalent bonds, the difference in electronegativity between the atoms determines the bond polarity.
A large electronegativity difference results in more polar bonds. For instance, in ammonia, the nitrogen atom is significantly more electronegative than hydrogen, causing the electrons to be pulled closer to the nitrogen.

• Determines the distribution of electron density.
• Key in predicting bond type.
• Differences in electronegativity above 0.4-0.5 often indicate polar bonds.

The concept of electronegativity difference is crucial in understanding the nature of chemical bonds and molecular interactions. It helps predict molecular behavior in different environments.

Covalent Bonds in Non-metals

Non-metal elements are known for forming covalent bonds due to their tendency to share electrons with each other to achieve stable noble gas electron configurations. This sharing allows both atoms to fill their outer shells without the transfer of electrons that characterizes ionic bonds.
In the ammonia molecule, both the nitrogen and hydrogen atoms are non-metals, naturally forming covalent bonds.

• Typical for non-metal to non-metal bonding.
• Includes both polar and nonpolar types.
• Found in many organic and inorganic substances.

Covalent bonds play a critical role in forming complex biological molecules. They provide stability and specificity in biological processes, underpinning the diverse range of organic chemistry.