The key difference between chalcophile and siderophile elements is that chalcophile elements occur near the surface of the earth, whereas siderophile elements occur near the core of the earth.
We can categorize all the chemical elements according to their source and distribution. And, this type of classification is called the Goldschmidt classification. As this method was developed by scientist Victor Goldschmidt, it is called Goldschmidt classification. The major categories in this classification include lithophile elements, siderophile elements, chalcophile elements, and atmophile elements.
CONTENTS
1. Overview and Key Difference
2. What are Chalcophile Elements
3. What are Siderophile Elements
4. Side by Side Comparison – Chalcophile vs Siderophile Elements in Tabular Form
5. Summary
What are Chalcophile Elements?
Chacophile elements are the chalcogen-loving elements. They are named as such because these chemical elements tend to combine with chalcogens (chemical elements in group 16) other than oxygen. Therefore, these elements can be observed near the surface of the earth. The members of this group include Ag, As, Bi, Cd, Cu, Ga, Ge, Hg, In, Pb, S, Sb, Se, Sn, Te, Ti, and Zn. There are metals and heavy nonmetals among these elements. They have a low affinity for oxygen, and they prefer to combine with other chalcogens. Mainly, we can find these elements in combination with sulfur atoms as sulfides, which are highly insoluble in water.
Typically, the sulfides of chalcophile elements are denser than the silicate minerals; therefore, they occur below the silicate minerals when crystallization of earth crust occurs. Therefore, it is rare to find these compounds on earth crust.
Figure 01: General Structure of Earth (from crust to core)
Among the members of the chalcophile element list, the most metallic elements are copper, zinc, boron group elements. Due to their metallic nature, these elements tend to combine with iron in the earth’s core. Moreover, chalcophile elements constitute the bulk of commercially important metals.
What are Siderophile Elements?
Siderophile elements are the transition metals that tend to sink to the core of the Earth. The sinking occurs mainly because these elements readily dissolve in iron in either the solid or molten state. The members of this list include Ru, Rh, Pd, Re, Os, Ir, Pt, and Au. In addition, Co, and Ni are included as moderately siderophile elements. However, some sources classify tungsten (W) and Ag as siderophile elements as well.
Figure 02: Gold is a Valuable Metal among Siderophile Elements
Practically, siderophile elements have no affinity for oxygen. E.g. oxides of gold are highly unstable. Sideophile elements can form strong bonds with sulfur and carbon atoms. Further, these elements can form metallic bonds with iron in earth’s core. Therefore, we can observe siderophile elements sunken in areas closer to the earth’s core. Most of the siderophile elements are thus considered as precious elements; e.g. gold, silver and platinum are of high expensive nature.
What is the Difference Between Chalcophile and Siderophile Elements?
We can categorize all the chemical elements according to their source. And, this type of classification is called the Goldschmidt classification. Chacophile elements are chalcogen-loving elements, while siderophile elements are the iron-loving elements. The key difference between chalcophile and siderophile elements is that chalcophile elements occur near the surface of the earth, whereas siderophile elements occur near the core of the earth. Moreover, chalcophile elements are typically less expensive than siderophile elements.
Below infographic tabulates more comparisons related to the difference between chalcophile and siderophile elements.
Summary – Chalcophile vs Siderophile Elements
Goldschmidt classification is a geochemical classification that groups chemical elements into four categories: lithophile elements, siderophile elements, chalcophile elements, and atmophile elements. The key difference between chalcophile and siderophile elements is that chalcophile elements occur near the surface of the earth whereas siderophile elements occur near the core of the earth.
Reference:
1. “Chalcophile Element.” Chalcophile Element – an Overview | ScienceDirect Topics, Available here.
2. “Goldschmidt Classification.” Wikipedia, Wikimedia Foundation, 11 May 2020, Available here.
Image Courtesy:
1. “Earth-crust-cutaway-English-Large label” By Earth-crust-cutaway-japanese.svg: Washiuchoderivative work: Brews ohare (talk) – Earth-crust-cutaway-japanese.svg (Public Domain) via Commons Wikimedia
2. “Gold nugget (placer gold) 1 (17001285916)” Par James St. John — Gold nugget (placer gold) 1,(CC BY 2.0) via Commons Wikimedia