reply to post by firepilot
I thought we were going to start playing nice. Ok, let the games begin........
All matter in the earth's crust is based on elements (in various chemical combinations).
There are 92 elements that occur naturally in the earth's crust (and a few very short-lived others that have been produced in laboratories).
These can be arranged by atomic number and by number of electron shells into something called the periodic table, which conveniently organizes all
these elements by their behavior into several groups.
You will be relieved to know that only about eight of these 92 elements are at all common in the rocks of the earth's crust (had you worried, didn't
I?):
i. Oxygen (O), with two shells and an atomic number of 8, is
far and away the most common element in the earth's crust,
making up about 47 percent of it by weight. It hangs out
the most with silicon, to form silica and the silicate
rocks that dominate the mantle and crust.
ii. Silicon (Si), with three shells and an atomic number of 14,
is the second most common element, making up about 28
percent of the earth's crust by weight. It hangs out with
oxygen to form silica (SiO2, which accounts for
just under 75 percent of the earth's crust!
iii. Aluminum (Al) is a light metal with three shells and an
atomic weight of 13 (pretty light). It makes up about 8
percent of the earth's crust, often as a part of silicate
minerals in the upper continental crust (e.g., feldspars,
remember "felsic" rock?).
iv. Sodium (Na) is another relatively light metal, with three
shells and an atomic number of eleven. It makes up not
quite three percent of the earth's crust and is often found
in silicate rocks (notably the plagioclase version of
feldspar, a light mineral in the upper continental crust).
It can also create an ionic bond with chlorine to form
table salt (or "halite"), and there is beaucoup of
it in the oceans (and, heck, your blood, your own portable
ocean).
v. Calcium (Ca), with four electron shells and an atomic
number of 20, makes up just under four percent of the
earth's crust. It often hangs out in silicate minerals,
such as plagioclase feldspar, and it often associates with
carbon and oxygen to form calcium carbonate (major
component of limestone and marble).
vi. Potassium (K) is another light metal with four shells and
an atomic number of 19. It makes up less than three
percent of the earth's crust and, like aluminum, it hangs
out in feldspar (but in a different form called
"orthoclase"). So, it is more common in the upper
continental crust.
vii. Iron (Fe) is a relatively heavier metal, with four electron
orbital shells and an atomic weight of 26. It makes up
about five percent of the earth's crust (becoming more
common with depth). As we saw earlier, it completely
dominates the earth's core (with nickel). It is also a
very common component of the mantle rocks and the oceanic
crust and the lower continental crust. There, it is
incorporated (often with magnesium) in the silicate
"ferromagnesian" minerals (such as olivine, pyroxene,
hornblende, and biotite).
viii. Magnesium (Mg) is a fairly light metal, with three shells
and an atomic number of 12. It only makes up about two
percent of the earth's crust, and it hangs out with iron a
lot, though, and is found in the "ferromagnesium" silicate
minerals.
ix. The remaining 84 naturally-occurring elements, then, only
make up 1.4 percent of the crust.
Did I tell you that I am a woman. We always win