Types of crystal
The physical properties of a material depend on its structure.
Materials in which the atoms or molecules have a regular arrangement (lattice) are called crystals.
There are four basic types of crystal:
ionic – a lattice formed by positively and negatively-charged ions.
metallic – a regular lattice of positively-charged metal ions surrounded by a ‘sea’ of delocalized electrons.
macromolecular (giant covalent) – a regular lattice of atoms held together by covalent bonds.
molecular (simple covalent) – a regular lattice of covalently-bonded molecules held together by intermolecular forces.
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The structure of diamond
Allotropes are different forms of the same element.
Diamond is an allotrope of carbon, and is an example of a macromolecular crystal.
Each carbon atom is bonded by covalent bonds to four other carbon atoms, creating a rigid, very strong 3D structure. 10 of 33
The structure of graphite
Graphite is another allotrope of carbon. Like diamond, it is a macromolecular crystal. However, it has very different physical properties because the carbon atoms are arranged in a different way.
Each carbon atom is covalently bonded to three others in the same 2D plane, forming layers.
These layers are held weakly together by van der Waals forces, not covalent bonds.
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Other allotropes of carbon
Another class of carbon compounds are the fullerenes.
Buckminsterfullerene is one type of fullerene. It contains 60 carbon atoms, each of which is bonded to three others by two single bonds and one double bond.
Carbon nanotubes are another type of fullerene. They are cylindrical carbon molecules. They have many potential applications, such as transporting drugs around the body and as components in electrical transistors.
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The structure of iodine
Solid iodine has a molecular structure consisting of a regular arrangement of iodine molecules (I2) held in place by van der Waals forces.
The melting point of iodine is low (387 K) compared to that of diamond, because less energy is required to break van der Waals forces than covalent bonds.
The structure of ice
In ice, water molecules form four hydrogen bonds with neighbouring water molecules, creating a repeating tetrahedral structure. Usually a solid is more dense than the same material in its liquid phase. However, cold water
(around 4 °C) is denser than ice.
hydrogen bond This is because not all the water molecules are hydrogen bonded, and the mean distance between molecules is less than the hydrogen bond length.
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Explain the structure of enzymes and discuss their metabolic reactions. Explain the structure of enzymes and discuss their metabolic reactions. Enzyme, a protein that catalyses a specific reaction. ‘Living cells contain thousands of different enzymes’ (Elliott, p.214), each of which catalyses (that is, accelerates without itself being changed) just one kind of reaction. In some of these reactions, small organic molecules such as amino acids, sugars, nucleotides, and lipids are broken down to…
art has a very unique and abstract style, with his structures ranging from being no taller than a few inches off the ground, to massive structures more than three times as tall as the average human being. “Melt to Earth” is currently on display around the Revson Fountain on Josie Robertson Plaza, located in Lincoln Center. The 14 metal structures are exhibited in a circle with various colors, designs and shapes. Aaron Curry’s tallest structure is the one of his most prominent pieces, towering above…
scale could be more developed to give a more accurate description of substances (Grunwald, 2014). Enzymes serve a catalyst, increasing the efficiency and speed of a chemical reaction, for biochemical reactions. Enzymes are made of various structures and amino acids. Nearly twenty percent of the human body is…
Chapter 2 Answers to examination-style questions Answers Marks Examiner’s tips 1 (a) and structure (of A) is complementary to A that of the active site; 1 You must be able to explain how enzymes act. (b) dea that non-competitive inhibitor (C) i binds at a site that is not the active site; binding causes a change in the shape of the active site; substrate is no longer able to bind to the active site; 3 Make sure that you know the different effects…
activates a appropriate response * Structure * Structural proteins give the cell mechanical support * Structural proteins keep the cell flexible and in their normal shape, as well as holding together the inside and membrane of the cell * Transport * Proteins are responsible for letting molecules in and out of the cell, and for carrying compounds in the body * Hemoglobin is a transport protein that carries oxygen Structure of Amino Acids Most of the proteins…
Adaption increases the long-term reproductive success of a species by helping its members to survive long enough to breed. Adaption and Selection are major features in evolution. Changes in DNA can result in two ways: 1. Changing the quantity or structure of the DNA of an organism. This is known as mutation. 2. Recombining the existing DNA of two individuals. This occurs due to sexual reproduction. DNA is the genetic material in bacteria. DNA is changing by mutations and conjugation. Mutations -Changes…
Reaffirmed 1998 ) lndian Standard CRITERIA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES (Fourth First Reprint Revision ) JULY 1999 UDC 699.841 : 624.042.7 0 Copyright 1986 BUREAU MANAK OF INDIAN 9 BAHADUR STANDARDS SHAH ZAFAR MARG BHAVAN, NEW DELHI 110002 Gr 14 June 1986 IS t 1893 - 1984 Indian Standard CRITERlA FOR EARTHQUAKE RESISTANT DESIGN OF STRUCTURES ( Fourth Revision ) Earthquake Engineering Sectional Committee, BDC 39 Chairman…
Why is CF mucus sticky? Mucus layer on the surface of the epithelial cells is sticky because it has less water than normal, this is because of less salt & water transport caused by a faulty protein channel. PROTEIN STRUCTURE: Antibodies, enzymes and many hormones are all protein molecules. Proteins also have functions within a membrane. Proteins are composed of amino acids, there are 20 different amino acids that occur in proteins. All amino acids contain an amine group -NH, a carboxylic acid…
painter used the line is such a way that it would reflect the shape of the woman who is the main character of the painting. It also tries to reflect other structure around her. The shape of the artwork informs us that the different organic shapes and even some geometric shapes have been used. The painter has used organic shape to paint the main character’s figures and shapes and she has also used geometric shape to reflect the other structures around her like tables and luggage bags. The use of light…
How does the structure of a protein dictate its function? The primary structure of any protein is determined by the number and sequence of amino acids. Each sequence of amino acids is specific for each protein. The secondary structure of a protein is based on hydrogen bonding. The C=O and -NH group on neighbouring amino acids will form many hydrogen bonds due to an unequal distribution of electrons in the bonds. The bonds causes polypeptide chains to twist into a three dimensional shape such as an…
