The answer to this is neon.
neon
Neon
helium
'Royal gas' is not a term used in chemistry. Perhaps you mean "noble gas", if so yes "inert gas" and "noble gas" often mean the same thing. However, oxides and fluorides of some of the "noble gasses " do exist, it might be best to think of them as "noble" rather than "inert". Xe, forms oxides.
Helium and argon are used as inert gases in welding.
Neon and sometimes argon
Noble Gases are useful because they make up chemical elements.
A noble gas is inert. However they sometimes sodium ions or mercury vapor.
the chemical element of number 10; an inert gaseous element of the noble gas group. It is obtained by the distillation of liquid air and is used in fluorescent lamps and signs
helium
An inert noble gas is used inside light bulbs.
'Royal gas' is not a term used in chemistry. Perhaps you mean "noble gas", if so yes "inert gas" and "noble gas" often mean the same thing. However, oxides and fluorides of some of the "noble gasses " do exist, it might be best to think of them as "noble" rather than "inert". Xe, forms oxides.
Helium and argon are used as inert gases in welding.
Inert gases are the noble gases (He, Ne, Ar, Kr, Xe, and Rn). They used to be called the inert gases until Neil Bartlett proved that you could make compounds out of some of them, so they were renamed "inert" gases.
Neon and sometimes argon
Noble Gases are useful because they make up chemical elements.
The noble gases are used in illuminated (aka Neon) signs. Refer to the related link to see an illustration of the colors made by the different noble gases.
The Group 18 elements are called the noble gases or sometimes inert gases. Wikipedia has information on the noble gases, and a link is provided.
Noble gases are considered inert because they have a full outer electron shell, making them stable and unlikely to undergo chemical reactions. They do not readily form compounds or ions with other elements due to their low reactivity. This stable electron configuration is the reason why noble gases are used in various applications, such as lighting, lasers, and filling balloons.