A member of the lanthanide, or rare earth, series of elements, holmium is a gray, somewhat shiny, soft metal. It is usually found in minerals containing several of the lanthanides. Because the rare earths all have the same outer electron shell configuration (6s2), their chemical properties are very similar, making it difficult to separate them from one another in the minerals in which they are usually complexed. They are best separated via repeated ion-exchange purification, a process developed in the United States during the 1940s.

Add another Use that has often been referenced. Helium is used as a mix with air in scuba tanks for deep dives to lessen the proportion of oxygen.

See this link:
http://www.pa.msu.edu/sciencet/ask_st/082593.html

Thanks for the great web page - SCSmith

The units of resistivity don't come out right.

10^-8 Ohm * m
or
m Ohm * cm

the 'm' should be a 'mu', but unfortunately they both look the same in the latin alphabet.

Why when breaking in a car a normal balloon will travel forwards but helium balloon will travel backwards?

In a letter to Nature [2004, 427, 225], E. Kim and M. H. W. Chan (Pennsylvania State University, USA) note that when liquid ⁴He is cooled below 2.176 K, it undergoes a phase transition and becomes a superfluid with zero viscosity. They claim that in addition to superflow in the liquid phase, superflow can also occur under some conditions in the solid phase of one of the helium isotopes (⁴He), and present results to back this up. In other words - evidence for a "supersolid". A supersolid behaves like a superfluid (flows without resistance) although it has crystalline solid characteristics.

See Nature for further datails.

Earth's most severe mass extinction - an event 250 million years ago that wiped out 90 percent of all marine species and 70 percent of land vertebrates - was triggered by a collision with a comet or asteroid, according to a team led by The University of Washington, Seattle, USA. Evidence is based upon elegant findings involving carbon molecules called buckminsterfullerenes (C₆₀, Buckyballs) with the gases helium and argon trapped inside their cage structures.

The scientists do not know the site of the impact 250 million years ago, when all Earth's land formed a supercontinent called Pangea. However, the space body left a calling card - a much higher level of complex carbon molecules called buckminsterfullerenes, or Buckyballs, with the noble (or chemically nonreactive) gases helium and argon trapped inside their cage structures. Fullerenes, which contain 60 or more carbon atoms and have a structure resembling a soccer ball or a geodesic dome, are named for Buckminster Fuller, who invented the geodesic dome.

The researchers know these particular Buckyballs are extraterrestrial because the noble gases trapped inside have an unusual ratio of isotopes. For instance, terrestrial helium is mostly helium-4 and contains only a small amount of helium-3, while extraterrestrial helium - the kind found in these fullerenes - is mostly helium-3.