Geochemical classification of elements

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Geochemical classification of Elements

• Prof. Fathy H. Mohamed
• By
• 1.Mahmoud Said El-sayed
• 2.Karim Mohamed Zaki
• 3.Ahmed Nasr Ahmed

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Geochemical classification of Elements

• Contents
• 1. Introduction
• 2. Goldschmidts Classification
• 3. Summary

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Introduction

• A classification that subdivides the chemical
  elements according to the criterion of their
  similaritythat is, their
• joint concentration in particular natural
  systems.
• The best-known geochemical classifications of the
  elements were put forth by the Norwegian
  geochemist V. M. Goldschmidt (1924) and the
  Russian geologists V. I. Vernadskii (1927), A. E.
  Fersman (1932), and A. N. Zavaritskii (1950).

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Goldschmidts classification

• The most widespread classification is probably
  that of Victor Goldschmidt. Goldschmidts scheme
  rests on the observation by Berzelius, a Swedish
  eighteenth-century chemist, that some elements
  tend to form oxides or carbonates whereas others
  form sulfides.

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Goldschmidts Classification
Goldschmidts classification

• . Using this periodic classification many
  successful predictions about the chemical
  behavior of the elements can be made. However,
  predictions about their geological behavior are
  less reliable. In the 1930's Goldschmidt
  developed a scheme to explain the distribution of
  the chemical elements on Earth. His methods were
  largely empirical.
• . He studied their distribution in meteorites,
  mixtures generated during smelting operations,
  and the compositions of silicate rocks, sulfide
  ores and native iron deposits .

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Goldschmidts Classification
Goldschmidts classification

• . His observations led him to classify the
  elements into four groups
• 1. lithophile Elements
• 2. Siderophile Elements
• 3. Chalcophile Elements
• 4. Atmophile Elements

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Goldschmidts Classification
Goldschmidts classification

• . Many meteorites are found to be subdivided into
  metallic, sulfide, and silicate phases, which
  presumably represent immiscible melts which
  formed when enough heat was available in the
  parent bodies to cause melting
• Meteorites are presumed to have an average
  composition similar to that of the primitive
  earth.
• . During the smelting of oxide and sulfide ores
  three different immiscible liquids form molten
  Fe, molten sulfides, and molten silicates

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Goldschmidts classification

• 1. Lithophile Elements
• are the elements of rock. As in the atoms of
  inert gases, there are eight electrons in each of
  the outer shells of their ions (in the lithium
  series there are two). They are difficult to
  reduce to the elementary state compounds with
  oxygen are most characteristic of them.
• The overwhelming majority of these elements are
  components of silicates.

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Goldschmidts classification

• The lithophile elements also occur naturally as
  oxides, halides, phosphates, sulfates, and
  carbonates.
• For the most part they are paramagnetic they
  lie on the descending parts of the atomic volume
  curve.
• They include 54 elements the alkali and alkaline
  earth metals boron, aluminum, and scandium the
  lanthanides and actinides (actinium, thorium,
  protactinium, and uranium) carbon, silicon,
  titanium, zirconium, hafnium, phosphorus,
  vanadium, niobium, tantalum, oxygen, chromium,
  and tungsten and the halogens and manganese
  (possibly technetium and astatine).

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Goldschmidts classification

• 2. Chalcophile ElementsThe chalcophile elements
  (according to Goldschmidt), or the thiophile
  elements (according to J. R. Hillebrand 1954),
• are the elements of the sulfide ores copper,
  silver, gold, zinc, cadmium, mercury, gallium,
  indium, thallium, germanium, tin, lead, arsenic,
  antimony, bismuth, sulfur, selenium, and
  tellurium.
• Their cations have 18 electrons in the outer
  shell (S2-, Se2-, and Te2- have eight electrons
  each)

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Goldschmidts classification

• In nature they are found as sulfides, selenides,
  tellurides, and thio salts (an exception is tin,
  which occurs as cassiterite, Sn02). Silver, gold,
  copper, arsenic, sulfur, bismuth, and some others
  occur naturally in the elemental forms.
• They are for the most part diamagnetic and lie on
  the ascending parts of the atomic volume curve.

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The atomic volume curve
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Goldschmidts classification

• 3. Sidrophile Elementsare elements with an
  electron shell that is being filled up. They
  include all the elements of Group VIII of the
  periodic system, as well as molybdenum and
  rhenium11 elements in all.
• They exhibit a specific chemical affinity for
  arsenicsperrylite, PtAs2 loellingite, FeAs2
  chloanthite, NiAs2 and cobaltite, CoAsSand a
  somewhat lesser affinity for MoS2 and othersas
  well as to phosphorus, carbon, and
  nitrogensulfurpentlandite, (Fe,Ni)9S8
  molybdenite,

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Goldschmidts classification

• 4. Atmophile Elmentsare the atmospheric
  elements.This group includes all the inert gases
  (from helium to radon), nitrogen, and
  hydrogeneight elements in all. The gaseous
  form is characteristic of them in nature. Most of
  the atmophile elements have atoms with closed
  outer electron shells and are situated in the
  upper parts of the .atomic volume curvethey
  are mainly diamagnetic. Occurrence in the natural
  state is characteristic of most of them (except
  for hydrogen, which closely resembles the
  lithophile elements).

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Goldschmidts classification

• Summary
• According to the classification given here, all
  the elements are distributed according to the
  most important natural genetic and paragenetic
  associations. The concepts of bio-phile
  (elements of living organisms) and
  thalassophile (seawater elements) are outside
  this classification.

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Goldschmidts classification

• 1-Siderophile elements those occur with native
  Fe and probably concentrated.
• 2-Chalcophile elements those concentrated in
  sulphides and characteristic of sulphide ore
  deposits.in the Earths
• 3-Lithophile elements those occur in silicates
  core.
• 4-Atmophile elements those are common in air
• and other natural gases
• In the periodic table siderophile elements are
• concentrated in the center of the table,
  lithophile elements to the left, chalcophile
  elements to the
• right and atmophile elements to the extreme right.

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Goldschmidts classification

• Geochemical Affinity
• In the classification scheme of Goldschmidt,
  elements are divided according to how they
  partition between coexisting silicate liquid,
  sulfide liquid, metallic liquid, and gas
  phasedefined by examining ore smelting slags
• Melting a chondrite gives 3 immiscible liquids
  plus vapor
• Metallic Liquid Siderophile
• Sulfide Liquid Chalcophile

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Goldschmidts classification

• Silicate Liquid Lithophile
• Gas Phase Atmophile
• Siderophiles - intermediate electronegativity,
  like .metallic bonding
• Lithophiles prefer ionic bonds
• Chalcophile - covalent bonding
• Atmophile - noble

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