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Groups 1A and 2A: the alkali and alkaline Earth elements
part of speciation and general behavior
24
Chemistry
Undergraduate 4
01/10/2017

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Term
base cations
Definition
the alkali and alkaline earth metals, more specifically the cations Na+, K+, Mg2+, and Ca2+
Term
the acidity or alkalinity of base cations
Definition
they are actually acid neutral
Term
why the cations Na+, K+, Mg2+, and Ca2+ are called base cations
Definition
because they don't hydrolyze to produce protons in the pH 4-9 range of soil solutions
Term
the oxidation state of the alkali metals (group 1A)
Definition
+I
Term
the valence of the alkali metals (group 1A)
Definition
monovalent
Term
which are stronger bases? group alkali metals or alkaline earth metals?
Definition
alkali metals
Term
the oxidation state of the alkaline earth metals (group 2A)
Definition
+2
Term
the valence of the alkaline earth metals (group 2A)
Definition
divalent
Term
why the alkali metals are considered strong bases
Definition
because their pKa values are >≈ 14
Term
why the alkaline earth metals are not considered strong bases
Definition
because their pKa values range from 11.44 and 13.47 exception: Be2+
Term
the dominant species in the soil solution
Definition
the divalent cations
Term
when the divalent cation is the dominant species in the soil solution
Definition
when the soil pH is less than approximately 11
Term
where the alkali and alkaline earth metals are primarily found
Definition
-aluminosilicate minerals
-carbonates
Term
how alkali metals are released into the soil solution
Definition
thru chemical weathering rxns
Term
how alkali metals exist in soil solution
Definition
they exist as free, uncomplexed, soluble monovatemt cations
Term
do alkali metals form soluble complexes with inorganic or organic ligands?
Definition
no
Term
the only retention mechanism for alkali metal cations
Definition
cation exchange
Term
why cation exchange is the only retention mechanism for alkali metal cations
Definition
because they do not form secondary mineral precipitates
Term
one way some cations, such as K+, Cs+, and NH4+ can become unavailable
Definition
fixation, in which they become trapped in a clay mineral, such as vermiculite, and become nonexchangeable
Term
what makes Be2+ unique among the alkali earth metals?
Definition
it forms neumerous hydrolysis products in pH > 5 solutions and has speciation similar to that of Al3+
Term
do alkaline earth cations form stable aqueous complexes with inorganic ligands?
Definition
yes
Term
some things alkaline earth cations form stable aqueous complexes with in the soil solution
Definition
-inorganic ligands
-soil organic matter
Term
do alkali earth cations form precipitates in soil?
Definition
they can, depending on geochemical conditions
Term
the divalent cations that dominate the cation exchange phase of soils
Definition
because they are generally the most abundant cations in soil sollutions
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