Use bond theory to differentiate between conductors, semiconductors and insulators.

In terms of electrical properties, materials can generally be classified into three main types: Conductors, Semiconductors, and Insulators. \n1. Conductors: These are materials that allow the easy flow of electricity. They have a lot of free electrons which can move freely, allowing the easy flow of current. Examples include metals like copper, aluminium. \n2. Semiconductors: These are materials whose conductivity lies between that of conductors and insulators. They do not have as many free electrons as conductors, but under certain conditions, they can have more free electrons and hence can conduct electricity. Examples include silicon, germanium. \n3. Insulators: These are materials that do not conduct electricity. They do not have free electrons that can move around, hence they do not allow the flow of electric current. Examples include rubber, wood, glass.

Bond theory explains these properties in terms of the types of bonds present: Conductors typically have metallic bonding, where electrons are not associated with individual atoms but are free to move around, giving rise to conductivity. Semiconductors have covalent bonding with atoms closely packed, so under certain conditions, the electrons can gain enough energy to jump from the valence band to the conduction band, allowing them to move and hence conduct electricity (this is called intrinsic conductivity). In insulators, the electrons are tightly bound to the atoms and are not free to move around, hence do not conduct electricity.

We can now correlate the bond theory with the properties of conductors, semiconductors and insulators. Conductors, with their mobile 'sea of electrons' due to metallic bonding, allow easy flow of electricity. Semiconductors, having covalent bonds, have fewer mobile electrons but can become more conductive under certain conditions when electrons can cross over from the valence band to the conduction band. Insulators, with their tightly bound electrons, are poor conductors of electricity. Thus, bond theory helps explain the electrical behaviors of conductors, semiconductors and insulators.