Difference Between Polymorphism and Allotropy

Thekey differencebetween polymorphism and allotropy is that the多态性发生在化学化合物中，而同素化合物发生在化学元素中。

Polymorphism is the presence of several different forms of the samesolid material. It means that the compounds of this type may have more than one晶体结构. Allotropy, on the other hand, is a similar chemical concept, but it describes the presence of several different forms of the same chemical element.

CONTENTS

1.Overview and Key Difference
2.What is Polymorphism
3.What is Allotropy
4.Side by Side Comparison – Polymorphism vs Allotropy in Tabular Form
5.概括

What is Polymorphism?

Polymorphism is the ability of a solid material to exist in more than one form or crystal structure. We can find this characteristic in anycrystallinematerial such as聚合物, mineral, metal, etc. There are several forms of polymorphism as follows:

• Packing polymorphism – depending on the differences in the crystal packing
• 构象多态性,the presence of different conformers of the same molecule
• Pseudopolymorphism – the presence of different crystal types as a result of hydration or solvation.

The variation of the conditions during the crystallization process is the main reason that is responsible for the occurrence of the polymorphism in crystalline materials. These variable conditions are as follows:

• 极性溶剂的
• Presence of impurities
• The level of supersaturation at which the material starts to crystalize
• Temperature
• Changes in stirring conditions

什么是同素拷贝？

Allotropy is the existence of two or more different physical forms of a chemical element. These forms exist in the same physical state, mostly in the solid state. Therefore, these are different structural modifications of the same chemical element. Allotropes contain atoms of the same chemical element that binds with each other in different ways.

Moreover, these different forms may have different physical properties because they have different structures and chemical behavior may vary as well. One allotrope may convert into another when we change some factors such as pressure, light, temperature, etc. Therefore these physical factors affect the stability of these compounds. Some common examples for allotropes are as follows:

• Carbon – diamond, graphite, graphene, fullerenes, etc.
• Phosphorous – white phosphorous, red phosphorous, diphosphorous, etc.
• Oxygen – dioxygen, ozone, tetraoxygen, etc.
• Boron – amorphous boron, alpha rhombohedral boron, etc.
• Arsenic – yellow arsenic, grey arsenic, etc.

What is the Difference Between Polymorphism and Allotropy?

Polymorphism is the ability of a solid material to exist in more than one form or crystal structure. It occurs only in chemical compounds. Moreover, it describes the differences in crystal structures of compounds. Allotropy is the existence of two or more different physical forms of a chemical element. It occurs only in chemical elements. In addition to that, it describes the differences in the atomic arrangement of compounds having the atoms of the same chemical element. The infographic below gives the difference between polymorphism and allotropy in a tabular form.

摘要 - 多态性与同种异体

多态性和同素异形是无机化学中的两个相关术语。多态性和同种异体之间的区别在于，多态性发生在化学化合物中，而同素化合物发生在化学元素中。

Reference:

1. “Polymorphism (Materials Science).” Wikipedia, Wikimedia Foundation, 3 July 2018.Available here
2.《百科全书》的编辑大不列颠。“同素。”2017年4月21日，英国百科全书，英国百科全书。Available here

Image Courtesy:

1.’Diamond and graphite’By User:Itub – Own work,(CC BY-SA 3.0)viaCommons Wikimedia