Helium: atomic number 2


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:

Thanks for the great web page - SCSmith

error in units

The units of resistivity don't come out right.

10^-8 Ohm * m
m Ohm * cm

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


Can anyone help me?

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

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