What are the two main ways that valence electrons participate in chemical bondin

Question

What are the two main ways that valence electrons participate in chemical bonding?

Diamond and graphite are both minerals comprised of carbon (C), but they have very different physical properties (esp. hardness). Why?

How does the external form of a crystal relate to its internal, atomic form (the arrangement of ions)?

Consider the different types of silicate structures. How does the arrangement of/link between the silica tetrahedral change from isolated to framework silicates (hint: bridging oxygen!)?

Why do minerals have cleavage? Give an example of a mineral that displays good cleavage.

Explanation / Answer

1- QUESTION FROM DIFFERENT SUBJECT

2-Both diamond and graphite are made entirely out of carbon, as is the more recently discovered buckminsterfullerene (a discrete soccer-ball-shaped molecule containing carbon 60 atoms). The way the carbon atoms are arranged in space, however, is different for the three materials, making them allotropes of carbon. The differing properties of carbon and diamond arise from their distinct crystal structures.In a diamond, the carbon atoms are arranged tetrahedrally. Each carbon atom is attached to four other carbon atoms 1.544 x 10-10 meter away with a C-C-C bond angle of 109.5 degrees. It is a strong, rigid three-dimensional structure that results in an infinite network of atoms. This accounts for diamond's hardness, extraordinary strength and durability and gives diamond a higher density than graphite (3.514 grams per cubic centimeter). Because of its tetrahedral structure, diamond also shows a great resistance to compression.

The carbon atoms in graphite are also arranged in an infinite array, but they are layered. These atoms have two types of interactions with one another. In the first, each carbon atom is bonded to three other carbon atoms and arranged at the corners of a network of regular hexagons with a 120-degree C-C-C bond angle. These planar arrangements extend in two dimensions to form a horizontal, hexagonal "chicken-wire" array. In addition, these planar arrays are held together by weaker forces known as stacking interactions. The distance between two layers is longer (3.347 x 10-10 meter) than the distance between carbon atoms within each layer (1.418 x 10-10 meter). This three-dimensional structure accounts for the physical properties of graphite.

5-If part of a crystal breaks due to stress and the broken piece retains a smooth plane or crystal shape, the mineral has cleavage. A mineral that never produces any crystallized fragments when broken off has no cleavage.

Example of good cleavage: Calcite

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