The Elements in Nature and
It is abundant in the universe since its simple atoms were the first "created" after the "Big Bang."
has the lowest density of any material, so it is only weakly held by the gravitational field of the
Fe in Fe
; Ca in CaCO
; Na in NaCl; Pb in PbS.
Differentiation is the separating of the materials of the earth into different regions (layers)
based primarily on their densities.
O, Si, Al, and Fe.
O. Si, Al, Ca, Na, K, and Mg are also present in the crust and mantle, but not in the core.
Groups IA and IIA and the left half of the transition metals are usually found as oxides, while the
right half of the transition metals and most of the p-block metals are found as sulfides. The more
electronegative metals tend to form sulfides, the less electronegative ones, oxides.
bauxite (impure Al(OH)
They are thermodynamically very stable. Great amounts of energy are needed for the production
of a metal from a silicate, making the process economically unfavorable.
Plant life has produced O
, which reacts with most metals. Plants need large amounts of K
growth, so have removed that ion from the crust.
Carbon atoms form a large number of bonds, which allows for the formation of a wide variety of
complex molecules necessary for life. Since C atoms are small, they form strong bonds with one
another, giving organic molecules stability, particularly with respect to reaction with O
Fixation is the process of converting an element in a form not directly usable by animals or plants
(usually in gaseous form) to a form which is usable (usually in condensed form). Nitrogen is fixed
from atmospheric N
and carbon is fixed from atmospheric CO
If too much CO
enters the atmosphere from human activities (primarily forest clearing,
decomposition of limestone, and burning of C-containing fuels), the possibility exists for an
unnatural warming of the earth due to trapping of heat by the "extra" CO
"Human activity and combustion." Production of compounds of Mg and Ca from dolomite,
production of steel and aluminum.
Nitrogen is removed from the atmosphere by atmospheric fixation on land and water, by
biological fixation on land, and by industrial fixation. The first involves reaction of N
induced by lightning, the second involves nitrogen-fixing bacteria, and the third involves reaction
in chemical plants to produce NH
and related compounds. Human activity is a significant
factor, contributing about 17% of the nitrogen removed.
Because N–N single bonds are weak, cyclic and chain compounds containing these bonds are not