Simple Explanation:
Intramolecular forces are the forces that hold together atoms in compounds. This page serves as a basic overview of bonding in chemistry.
Ionic Bonds
Definition: Ions of opposite charges held together by electrostatic attraction.
Physical State: Forms crystal lattice structures of ions.
Polarity: Ionic bonds are very polar.
Solubility: Has relatively high solubility in polar solvents, where it can dissociate into ions.
Intermolecular Forces: Strong intermolecular forces due to electrostatic attraction between ions of opposite charges.
Conductivity:
As a liquid or in an aqueous state: Conductive due to freely-moving ions from overcoming intermolecular forces.
As a solid: Not conductive, as ions are locked in place.
Physical Property: Hard yet brittle, as shifting the ions' positions easily results in repulsion.
Covalent Bonds
Definition: Chemical bonds that involve the sharing of valence electrons.
Each bond consists of two electrons.
Types of Covalent Bonds:
All covalent bonds have a σ-bond, which is a direct bond between two orbitals facing each other on the same axis.
Single bonds: Consists of one σ-bond. Total of two valence electrons shared.
π-bonds are formed by the side-by-side overlap of p-orbitals, which are perpendicular to the axis connecting the nuclei of the bonded atoms.
Double bonds: Consists of one σ-bond and one π-bond. Total of four valence electrons shared.
Triple bonds: Consists of one σ-bond and two π-bond. Total of six valence electrons shared.
Polarity: Covalent bonds can be either polar or nonpolar, depending on the electronegativity difference between the bonded atoms of compounds.
Intermolecular Forces: Generally has weaker intermolecular forces than most ionic and metallic compounds.
Conductivity: Usually poor conductors, as most covalent compounds don't dissociate or possess delocalized electrons.
Physical States:
Molecular Compounds: Usually exists as a gas, a liquid, or a solid with a low melting-point.
Covalent Network Solids: Usually exist as solids with high melting points. Unlike molecular compounds, which are composed of discrete units, they form a continuous network of covalently bonded atoms.
NOTE: Ionic and Covalent Bonds Exist on the Same Spectrum
Properties of chemical bonds lie on a spectrum, influenced by the difference in electronegativity between atoms. Electronegativity, which indicates how strong an element's nucleus pulls on valence electrons, dictates the polarity and type of bond formed.
A more uneven difference in electronegativity between two atoms cause a more polar bond due the difference in "pull" strength for their valence electrons. Conversely, a more even difference means that the electrons will be shared more evenly.
Since it is a spectrum, there are no clear boundaries between these values. As a result, some compounds can exhibit both ionic and covalent properties.
Metallic Bonds
Definition: Occur between metal atoms where electrons are free to move throughout a lattice of positive ions.
Intermolecular Forces: Strong intermolecular forces due to electrostatic attraction between the ions and the
Polarity: Metallic bonds are considered nonpolar due to the delocalized, nondirectional "sea" of electrons.
Solubility: Depends on reactivity. More reactive metals may undergo redox reactions with solvents, forming aqueous ions.
Conductivity: Highly conductive due to the delocalized electrons within the metal.
Physical Property:
Malleable and ductile due to its delocalized electrons.
Has relatively higher luster. More inert metals reflect more light due to resistance from oxidation.
Metallic Alloys:
Substitutional Alloy: Metallic elements with similar atomic radii replace atoms in the host metal's lattice, forming a relatively uniform structure. (e.g. brass, composed of copper and zinc)
Interstitial Alloy: Smaller atoms fit into the spaces between larger metal atoms in the lattice. (e.g. steel, consisting of iron and carbon)