The wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
In summary, gravity is the force that creates the pressure to fuse atoms, which makes the stars shine. Eventually the temperature is high enough that the star starts fusing hydrogen into helium. When the outward pressure produced by the heating of the gas by fusion energy balances gravity, a stable star is formed.
Yes, in general, metalloids are slightly reactive.
Vanadium is my favourite element because valadium alloys are used in nuclear reactors, valdium is also used for some ceramics and glass, its essential to some species (including humans although we need very little) an example of this is valafium is used to treat diabetes and low blood sugar