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

Molecule

The fundamental unit of a compound that retains its properties are known as molecules. Molecules are made up of two or more atoms. We know that an atom is the smallest unit of matter but a molecule is the smallest unit that can retain both the physical as well as chemical properties. Molecules can be broken into their constituents, i.e., the atoms that make up the molecules.

Examples of molecules

A molecule is usually composed of two or more atoms that form the smallest unit which can be recognized.

H2O (water)
O3 (Ozone)
CaO (Calcium oxide)
NaCl (salt)

Shape of a Molecule: VSEPR Theory

The covalent molecules have a particular three-dimensional structure. The shape and structure of a specific molecule can be understood by its covalent bonds. The ones that are made of electrons are negatively charged. It starts to repel each other. This theory is known as valence shell electron pair repulsion (VSEPR).

Example: In BeCl2, the molecules are bonded by covalent bonds. They stay as far from each other in the absolute opposite directions as possible, which are 180 in angle. It produces a linear molecule. In BF3 as well, three covalent bonds are present which repel one another to construct an angle of 120 in a plane.

Compound

Compounds are defined as substances that are formed when two or more elements mix chemically, keeping the ratio of mass constant. It contains two or more elements. Various kinds of elements that occur in a constant ratio of atoms make up compounds. The individual properties of elements diminish when they mix, and new characteristics are formed of the new product.

Chemical Formula: Chemical formula is the symbolic representation of the compounds. It shows the proportion of atoms that are contained in a compound. The chemical formula for normal salt is NaCl while the one for water is H2O. H2O of water represents that one molecule of water contains two atoms of hydrogen and one atom of oxygen. Similarly, the chemical formula of salt 'NaCl' represents that one atom of sodium and one atom of chlorine is present in a molecule of sodium chloride.

Types of Compounds

Compounds are mainly classified into two subtypes: salts and molecular compounds. Molecular compounds - In these compounds, the atoms bind each other through covalent bonding. Example: NH3, CH4. Salts - The atoms in salt are bound together through ionic bonding. Example: NaCl