Nickel is a chemical element, with the
chemical symbol Ni and it has an atomic number of 28.
The atomic weight of nickel is 58.6934. 
Things you might not know about
Nickel:
1. Nickel
is chiefly valuable in the modern world for the alloys it forms.
About 60% of world production is used in nickel-steels
(particularly stainless steel).
2. It is
one of only four elements that are magnetic at or near room
temperature.
3. During
the wartime period 1942–45, nickel was removed from Canadian
and U.S. coins entirely, due to nickel's war-critical use in armor
plating.
4. The US
nickel coin contains 0.04 oz (1.25 g) of nickel, which at the April
2007 price was worth 6.5 cents, along with 3.75 grams of
copper worth about 3 cents, making the metal value over 9
cents.
See GC2XAY2 - Hydrogen, for an explanation
about this series of caches.