The answer to whether helium conducts electricity depends entirely on its physical state. Under standard conditions, such as room temperature and atmospheric pressure, helium gas is an excellent electrical insulator. As a colorless, odorless, and non-toxic noble gas, it actively resists the flow of electric current. This resistance makes gaseous helium an extremely poor conductor, a property it shares with many other gases.
Atomic Structure and Resistance to Conduction
Electrical conduction requires the movement of charged particles, typically free electrons or ions, through a material. The atomic structure of helium prevents this movement under normal circumstances, causing it to behave as an insulator. A helium atom has two protons and two electrons, which completely fill the atom’s outermost and only electron shell.
This filled shell represents a state of maximum stability, defining helium as a noble gas. Atoms tend toward this stable configuration, making them chemically inert. For an electrical current to flow, atoms must readily give up or accept electrons to provide mobile charge carriers. Since helium atoms hold onto their electrons tightly, they do not produce the free electrons or ions required for electrical conduction, presenting a high resistance to electric current.
The Transition to a Conductor: Ionization and Plasma
The insulating nature of helium is not absolute, as extreme conditions can force the atom to become an effective electrical conductor. This transition occurs through ionization, where enough energy is applied to strip one or both electrons from the atom. The first ionization energy for helium is exceptionally high—the highest of any element on the periodic table. This high energy requirement reflects the stability of its electron shell.
When this substantial energy is applied, typically through intense heat, a strong electric field, or high-energy radiation, the gas changes into plasma. Plasma is often referred to as the fourth state of matter. It is an electrically neutral, gas-like cloud composed of free electrons and positively charged helium ions. The presence of these unbound charged particles completely changes the electrical properties of the substance.
In this plasma state, the liberated electrons and ions move freely and respond to an applied voltage, allowing electric current to flow easily. This results in plasma being a highly conductive medium. Even if the helium is only partially ionized, the concentration of mobile charged particles is sufficient to transform the gas from an insulator into a conductor. This conductive plasma state is the most common form of helium found in the universe, making up a significant portion of stars and other celestial bodies.
Applications Utilizing Ionized Helium
The conductive properties of helium plasma are utilized in several advanced technological and scientific applications. One common use is in specialized lighting and display technology, such as discharge tubes. When a high voltage is applied across a tube filled with low-pressure helium gas, the gas ionizes and emits a characteristic reddish-orange glow as the electrons recombine with the ions.
In industrial settings, helium is used to create thermal plasmas for processes like plasma arc welding. The conductive gas facilitates the stable and extremely hot arc necessary for joining metals. The ability to create and control highly conductive helium plasma is important in fusion energy research. Experiments in devices like tokamaks use helium plasma as a medium to study the conditions required for sustained nuclear fusion reactions.