Molecule vs Lattice
Atoms join together to form various chemical substances. According to their arrangement their properties change.
Molecules are made up by chemically bonding two or more atoms of the same element (e.g.: O2, N2) or different elements (H2O, NH3). Molecules don’t have charge, and the atoms are bonded by covalent bonds. Molecules can be very large (hemoglobin) or very small (H2), depending on the number of atoms that are connected. The type and number of atoms in a molecule are shown by the molecular formula. The simplest integer ratio of atoms present in a molecule is given by the empirical formula. For example, C6H12O6 is the molecular formula of glucose, and CH2O is the empirical formula. Molecular mass is the mass calculated considering the total number of atoms given in the molecular formula. Each molecule has its own geometry. The atoms in a molecule are arranged in a most stable manner with a specific bond angle and bond lengths to minimize the repulsions and straining forces.
Lattice is a mathematical phenomenon. In chemistry, we can see different types of ionic and covalent lattices. Latice can be defined as a solid that has a three- dimensional ordered arrangement of basic units. The basic unit can be an atom, molecule or an ion. Lattices are crystalline structures with these repeated basic units. When ions joined with ionic bonds, they form ionic crystals. For example, sodium chloride can be taken. Sodium is a group 1 metal, thus forms a +1 charged cation. Chlorine is a nonmetal and has the ability to form a -1 charged anion. In the lattice, each sodium ion is surrounded by six chloride ions, and each chloride ion is surrounded by six sodium ions. Due to all the attractions between ions, the lattice structure is more stable. The number of ions present in the lattice varies with the size of it. Lattice energy or enthalpy of lattice is the measure of the strength of the ionic bonds in the lattice. Normally lattice enthalpy is exothermic.
Diamond and quartz are two examples for three dimensional covalent lattices. Diamond is composed of only carbon atoms, and each carbon atom is covalently bonded to four other carbon atoms to form the lattice structure. So each carbon atom has the tetrahedral arrangement. Diamond has gained high stability by forming a structure like this. (Diamond is known to be one of the strongest minerals.) Quartz or silicon dioxide also has covalent bonds, but they are between silicon and oxygen atoms (lattice of different atoms). Both of these covalent lattices have a very high melting point, and they cannot conduct electricity.
Difference Between Molecule and Lattice
- Lattices have very high molecular weights than the molecules.
- Molecules have a definite structure with a molecular formula, but lattice structure size varies according to the number of repeating units it has. However, the repeating units of a lattice have atoms or ions in a definite ratio.
- Water is a molecule, and when it freezes, it takes a regular arrangement forming a lattice.
- Lattices have a three-dimensional structure, but molecules don’t.
- Lattices are solids, but molecules can be either solid, gas or liquid.