Question

Write a chemical formula for each substance, and draw a picture of how the nanoscale particles are arranged at room temperature. (a) Water, a liquid whose molecules contain two hydrogen atoms and one oxygen atom each (b) Nitrogen, a gas that consists of diatomic molecules

Short answer

Water: \( H_2O \), liquid; Nitrogen: \( N_2 \), gas.

Step-by-step solution

Determine Chemical Formula for Water

Water is a simple molecule composed of two hydrogen atoms and one oxygen atom. Therefore, the chemical formula for water is \( H_2O \).

Visualize Nanoscale Particles in Water

In liquid water at room temperature, water molecules are closely packed but move freely. Each \( H_2O \) molecule interacts with nearby water molecules through hydrogen bonds, resulting in a fluid structure without fixed shape.

Determine Chemical Formula for Nitrogen

Nitrogen gas consists of diatomic molecules, meaning each molecule is composed of two nitrogen atoms. Thus, the chemical formula for nitrogen is \( N_2 \).

Visualize Nanoscale Particles in Nitrogen

At room temperature, nitrogen gas molecules are spaced apart in a random distribution and move rapidly. Each \( N_2 \) molecule exists independently, with large gaps between them, characteristic of a gas state.

Key concepts

Molecular Structure

The molecular structure of a substance refers to how its atoms are arranged and connected. In the case of water (H₂O), each molecule consists of two hydrogen atoms bonded to a single oxygen atom. This creates a bent shape due to the arrangement of electron pairs around the oxygen. On the other hand, nitrogen gas (N₂) is composed of diatomic molecules, where two nitrogen atoms form a triple bond. This triple bond is very strong and linear in structure.
Understanding molecular structure is crucial because it influences the physical and chemical properties of substances. For example, the bent shape of water molecules gives rise to its polar nature and unique properties like high surface tension and boiling point.

Nanoscale Visualization

Visualizing substances at the nanoscale helps us understand how molecules interact at a very small level. At the nanoscale, we can picture how water molecules form a network through hydrogen bonds, holding them together despite their mobility. This is why water stays liquid under normal conditions.
For nitrogen, nanoscale visualization would show nitrogen molecules as separate entities moving rapidly in different directions, characterizing its gaseous state. Unlike water, nitrogen's molecules do not interact strongly with each other, leading to its widespread distribution and occupancy in the atmosphere.

Hydrogen Bonds

Hydrogen bonds are a type of weak interaction that occurs when a hydrogen atom, covalently bonded to an electronegative atom like oxygen, comes close to another electronegative atom. In water molecules, hydrogen bonds form between the hydrogen atom of one water molecule and the oxygen atom of another. This bond is much weaker than a covalent bond but significantly impacts the properties of water.
These bonds are responsible for many of water's unique characteristics, such as its high boiling point, surface tension, and ability to dissolve many substances. The presence of hydrogen bonding in water explains why it forms a cohesive and dynamic liquid structure at room temperature.

Diatomic Molecules

Diatomic molecules consist of two atoms. In the case of nitrogen gas (N₂), each molecule consists of two nitrogen atoms connected by a strong triple bond. Most diatomic molecules are linear and have simple formulas like oxygen (O₂) and hydrogen (H₂).
These molecules are often gases at room temperature due to the lack of strong intermolecular forces, allowing them to spread out and fill available space. Diatomic gases are crucial for life and technology, playing roles in everything from respiration to manufacturing processes.