Difference Between Molecules and Compounds: Examples, Shape, Types, and VSEPR Theory

Molecule

A molecule is the fundamental unit of a compound that retains its properties. Molecules are composed of two or more atoms bonded together. While an atom is the smallest unit of matter, a molecule is the smallest unit that retains both physical and chemical properties. Molecules can be broken down into their constituent atoms.

Examples of Molecules:

H2O (Water)
O3 (Ozone)
CaO (Calcium oxide)
NaCl (Salt)

Shape of a Molecule: VSEPR Theory

Covalent molecules have a specific three-dimensional structure. The shape and structure of a molecule can be understood through its covalent bonds, which are made of electrons that are negatively charged and repel each other. This concept is explained by the Valence Shell Electron Pair Repulsion (VSEPR) theory.

Examples:

BeCl2: The molecules are bonded by covalent bonds and arrange themselves as far apart as possible, resulting in a linear shape with a 180° bond angle.
BF3: The three covalent bonds repel each other to form a planar molecule with 120° bond angles.

Compound

Compounds are substances formed when two or more elements chemically combine in a fixed mass ratio. Compounds consist of two or more different elements, and when they mix, the individual properties of the elements change, creating new characteristics.

Chemical Formula: The chemical formula represents the proportion of atoms in a compound. For example:

H2O: Represents water, with two hydrogen atoms and one oxygen atom.
NaCl: Represents salt, with one sodium atom and one chlorine atom.

Types of Compounds

Compounds are mainly classified into two subtypes:

Molecular Compounds: Atoms are bound together through covalent bonds. Examples: NH3 (Ammonia), CH4 (Methane).
Salts: Atoms are bound together through ionic bonds. Example: NaCl (Salt).

Difference between Molecules and Compounds

Molecules	Compounds
Formed by two or more atoms bonded by chemical bonds.	Formed by two or more elements mixed in fixed ratios.
Not all molecules are compounds.	All compounds are molecules.
Examples: Ozone (O3), Nitrogen (N2).	Examples: Table salt (NaCl), Ammonia (NH3), Methane (CH4).
Structurally, composed of two or more atoms held by strong forces.	Classified as matter with definite shape.
Cannot be seen with the naked eye due to their atomic scale.	Can be seen with the naked eye.

Summary

Molecules are generally composed of at least two atoms bonded by strong forces. Compounds are formed from various elements combined in fixed proportions, resulting in new properties distinct from the individual elements.

FAQs: Difference Between Molecules and Compounds

1. What is a molecule?
A molecule is the fundamental unit of a compound that retains its properties and is composed of two or more atoms bonded together.

2. Can you give examples of molecules?
Examples of molecules include:

H2O (water)
O3 (ozone)
CaO (calcium oxide)
NaCl (salt)

3. How is the shape of a molecule determined?
The shape of a molecule is determined by its covalent bonds and the repulsion between electron pairs, described by the Valence Shell Electron Pair Repulsion (VSEPR) theory.

4. What is VSEPR theory?
VSEPR (Valence Shell Electron Pair Repulsion) theory explains that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion, determining the molecule's shape.

5. What is an example of a molecule's shape explained by VSEPR theory?
In BeCl2, the molecule is linear with a bond angle of 180 degrees. In BF3, the molecule forms a planar shape with bond angles of 120 degrees due to repulsion between three covalent bonds.

6. What is a compound?
A compound is a substance formed when two or more elements mix chemically in a fixed mass ratio. Compounds have different properties than the individual elements they are made from.

7. How is the chemical formula of a compound represented?
The chemical formula shows the proportion of atoms in a compound. For example, H2O represents water with two hydrogen atoms and one oxygen atom. NaCl represents sodium chloride (table salt) with one sodium atom and one chlorine atom.

8. What are the types of compounds? Compounds are classified into two main types: