Chemical Bonding and Ionic Bonds

Study Notes

A chemical bond is an electrostatic force holding atoms together in a compound.
A bond forms when the atoms are closer together than when apart, leading to a lower energy state.
There are three types of bonding: Ionic, Metallic, and Covalent.

Ionic compounds have a three-dimensional lattice structure, with ions held together by electrostatic attraction.
Electrons are transferred, forming cations (positively charged) and anions (negatively charged) ions.
The strength of attraction depends on the size and charge of the ions.
Larger electronegativity differences (typically >2) result in ionic bonds.
Ionic compounds are often formed between elements from Groups 1 and 2 with elements from Groups 16 and 17.
Lattice energy represents the strength of the ionic attraction, influencing properties like melting point, hardness, and solubility.
Ionic compounds are typically hard, crystalline, brittle solids with high melting points.
They do not conduct electricity as solids but can conduct electricity when molten or dissolved.

Metallic bonding occurs when elements have low ionization energies, allowing valence electrons to become mobile.
This creates a "sea of electrons" surrounding the metal cations, holding them together.
Metals are good electrical conductors in both solid and molten states.
Metals are malleable and ductile because atoms can move past each other within the electron sea.
Melting points vary, but are often relatively low as the electron sea maintains attraction between nuclei and electrons.
Boiling points are typically high due to the strong attraction between the nuclei and electron sea.

Electrons are shared between atoms in covalent bonds.
The bond length is the specific distance between bonding nuclei where the molecule's energy is minimized.
A single covalent bond consists of a pair of shared electrons.
Double bonds occur when two pairs of electrons are shared, and triple bonds involve three pairs of shared electrons.
Lone pairs or non-bonding pairs are valence electrons that don't participate in bonding.
Polar covalent bonds arise when the electron pair is attracted more strongly to the atom with higher electronegativity.
The atom with higher electronegativity gains a partial negative charge, while the atom with lower electronegativity has a partial positive charge.
There is an inverse correlation between bond strength and bond length.
Stronger bonds generally have shorter bond lengths.