Molecule

Definition

A molecule is the smallest unit of a chemical compound that retains its unique chemical properties and composition. It is composed of two or more atoms bonded together, forming the basic building blocks of matter.

5 Must Know Facts For Your Next Test

1. Molecules can be composed of atoms of the same element (e.g., O₂, N₂) or different elements (e.g., H₂O, CO₂).
2. The type and arrangement of atoms in a molecule determine its chemical properties and reactivity.
3. Molecules can exist in different phases (solid, liquid, gas) depending on the strength of intermolecular forces and the thermal energy present.
4. The polarity of a molecule, determined by the distribution of electrons, affects its interactions with other molecules and its physical properties.
5. Molecular shape, as described by the Valence Shell Electron Pair Repulsion (VSEPR) theory, is a key factor in determining a molecule's chemical behavior.

Review Questions

• Explain how the composition and structure of a molecule relate to its physical and chemical properties.
  • The composition and structure of a molecule, including the types and arrangement of atoms, the chemical bonds, and the overall molecular shape, directly influence its physical and chemical properties. For example, the polarity of a molecule, determined by the distribution of electrons, affects its intermolecular interactions and determines its state of matter (solid, liquid, or gas) at a given temperature and pressure. Similarly, the strength and type of chemical bonds within a molecule dictate its reactivity and the types of chemical reactions it can undergo.
• Describe how the concept of a molecule is connected to the classification of matter.
  • Molecules are the fundamental building blocks of matter, and their properties and interactions are central to the classification of matter. The composition and structure of molecules determine the physical and chemical properties of substances, which can then be used to categorize matter into different states (solid, liquid, gas) and types (pure substances, mixtures). For instance, the intermolecular forces between molecules influence the phase of a substance, while the chemical bonds within molecules determine their reactivity and ability to form new compounds, which is a key aspect of the classification of matter.
• Analyze how the behavior and properties of molecules can be used to explain the various phases of matter and the transitions between them.
  • The behavior and properties of molecules, such as their intermolecular forces and the strength of their chemical bonds, are directly linked to the different phases of matter and the transitions between them. For example, the relatively weak intermolecular forces in gases allow the molecules to move freely and occupy a large volume, leading to the gaseous state. In contrast, the stronger intermolecular forces in liquids and solids restrict the movement of molecules, resulting in the more compact liquid and solid states. The phase transitions, such as boiling, melting, and condensation, can be explained by the changes in the balance of intermolecular forces and the energy required to overcome them as the temperature or pressure of the system is altered.

Related terms

Atom:

The fundamental unit of an element, consisting of a nucleus containing protons and neutrons, with electrons orbiting the nucleus.

Chemical Bond: The attractive force that holds atoms together in a molecule, resulting from the sharing or transfer of electrons between atoms.

Intermolecular Forces:

The attractive or repulsive forces that exist between molecules, influencing the physical properties and behavior of substances.