Chemistry: Bonding and Structure

Chemical Bonding

Chemical bonding refers to the process where atoms combine together to form more complex structures like molecules and compounds.
There are three main types of chemical bonding: ionic bonding, covalent bonding and metallic bonding.
Ionic bonding occurs when electrons are transferred from one atom to another. This typically happens between metals and non-metals, where the metal loses electrons to become a positively charged ion, and the non-metal gains electrons to become a negatively charged ion.
Covalent bonding involves the sharing of electrons between atoms. This generally occurs between non-metal atoms.
Metallic bonding involves the sharing of electrons among a lattice of positively charged metal ions, leading to properties such as electrical conductivity and malleability.

Polarity in a chemical bond is due to a difference in electronegativity - the ability of an atom to attract the shared pair of electrons in a covalent bond.
The greater the difference in electronegativity between two bonded atoms, the more polar the bond.
If there is a significant difference in electronegativity, the bond may be ionic rather than covalent.

The Lewis Structure is a simple model used to represent the arrangement of atoms and electrons within a molecule or an ion. It specifically shows how valence electrons are arranged among the atoms in the molecule.
VSEPR (Valence Shell Electron Pair Repulsion) theory explains the shape of molecules based on the principle that electron pairs will arrange themselves to minimise repulsion.
The shape of the molecule influences its properties, such as reactivity and polarity.

Intermolecular forces are the forces of attraction between different molecules, and can either be van der Waals forces, dipole-dipole interactions, or hydrogen bonding.
Van der Waals forces, also known as London dispersion forces, are present between all molecules, and increase with the size of the molecule.
Dipole-dipole interactions occur between polar molecules, where the positive end of one molecule is attracted to the negative end of another molecule.
Hydrogen bonding is a special form of dipole-dipole interaction, and occurs where a hydrogen atom is covalently bonded to a highly electronegative atom such as nitrogen, oxygen or fluorine, and is also in close proximity to another electronegative atom.

The properties of a substance can be largely attributed to its bonding and structure - for example, ionic compounds typically have high melting and boiling points due to the strong electrostatic forces between ions, while covalent compounds might exist as small molecules with low melting and boiling points due to weak intermolecular forces.
Other properties that can be determined by the type of bonding include solubility in water, conductivity, hardness, and reactivity.