The handle of the titanium mug in Figure 1 was joined to the body by welding. The pieces were heated until their surfaces fused together. The welding of titanium does not take place in air. At the temperature at which welding occurs, titanium becomes hot enough to react with oxygen in the air, forming an oxide. The oxide makes the weld more brittle and likely to break. Because titanium does not react with a noble gas such as argon, the welding of titanium usually takes place in an argon atmosphere.

Figure 1  The handle and body of this titanium mug were welded together in an argon atmosphere. If titanium is allowed to react with oxygen in air, the compound that forms makes the weld more brittle and more likely to break.

Argon's name is a reminder of its inactivity. It comes from the Greek word argos, which means “idle” or “inert.” Why is argon very inactive yet oxygen is highly reactive? Chemical properties, such as reactivity, depend on an element's electron configuration.