How does a neon sign work?

Neon is a stable gas found in large quantities in the universe, but only as a small percentage of Earth's atmosphere.

A neon light consists of a glass tube filled with a small amount of one or more noble gases/elements in a vacuum connected to an electrical circuit.

There is electrode at each end of the glass tube, which contains the noble gases that light up. A neon light is activated either by AC (AC) or DC (DC). AC (AC current) is used in the vast majority of neon signs. 

It is a common misconception that all neon signs contain only neon gas. A neon sign containing only neon gas will light red-orange when placed in a vacuum connected to an electrical circuit.  

If the sign is to light up in other colours, it requires mixing other gases and elements in the glass tubes. The most commonly used are argon, mercury, krypton, helium and xenon.

When powering argon, the neon sign will light up in lavender color. And if you add a small drop of mercury, the neon sign will instead light up ultraviolet. Helium produces orange-and-white light. Krypton creates a greenish light and Xenon creates neon signs in a blue-gray color.

 

Technical explanation of neon lights

One of the characteristics of the elements used in neon signs is that each atom has an electron shell that is filled. This means that the atoms cannot react with other atoms. It takes a lot of energy to remove an electron.

When electrical voltage (more than 10,000 volts) is sent through the electrodes in the neon sign, enough energy is supplied to remove an outer electron from the neon atom (as well as the atoms in the other elements used in neon signs). If the voltage is too low, not enough kinetic energy will be produced for the electrons to release the atoms and the neon sign will not light up.

When there is sufficient voltage, the positively charged neon atoms will be attracted to the negative electrode in the neon sign and the free electrons will be attracted to the positive electrode. The charged particles create the electrical circuits of the neon light.

The very light in a neon sign is created by the atoms moving around and bumping into each other inside the glass tube, thus transferring energy to each other and creating high heat.  

Some electrons managed to escape their atoms, while others get enough energy to become so-called "excited", which means that they achieve a higher energy state. When the electrons use the extra energy, they release a photon or light particle, which is what creates the neon light