Molecule is a whole composed of atoms in accordance with a certain bonding order and spatial arrangement, which is called molecular structure. Due to the interaction between atoms in a molecule, the physical and chemical properties of a molecule depend not only on the type and number of atoms, but also on the structure of the molecule.

Molecule is the smallest unit that can exist independently and keep the physical and chemical properties of a substance. Molecules are made up of atoms, which combine into molecules in a certain order and arrangement through a certain force. Take the water molecule as an example, water is separated continuously until the characteristics of water are not destroyed. At this time, the smallest unit is a water molecule (H2O) composed of two hydrogen atoms and one oxygen atom.

Source: @liinohxtattoo