Why are metals good conductors of heat and electricity?

Metals are considered good conductors of heat and electricity primarily because they contain free-moving electrons. In metallic structures, the atoms are arranged in a lattice formation, with some of the electrons being delocalized. This means that the electrons are not bound to any specific atom and can move freely throughout the metal.

When heat is applied to a metal, these free electrons gain energy and start to move more actively, transferring kinetic energy across the material. This movement of electrons is what allows metals to efficiently conduct heat. Similarly, when an electric field is applied, these free electrons can flow easily through the metal, resulting in electrical conduction.

The other choices do not accurately describe why metals are good conductors. A fixed structure does not allow for the movement of electrons; ionic bonds refer to a different type of bonding typically found in compounds rather than in metals, and being made of gases does not relate to the conductive properties of metals, since metals are solid at room temperature and have a crystalline structure.