Group 2 chemical properties (chapter 11 - part 2):
• Group 2 burns in presence of oxygen forming metal oxides
• Group 2 oxides dissolve in water giving alkaline solution
• We can use flame color test to identify group 2 elements
• Beryllium reacts with steam water at high temperature forming beryllium oxides and hydrogen
• Calcium readily reacts with water forming hydroxides and hydrogen
• Group 2 alkalinity of group 2 hydroxides increases down the group due to the increase in solubility
• Solubility of group 2 sulfates decreases down group 2
• All group 2 carbonates are insoluble in water except for Beryllium
• All group 2 reacts with dilute acid forming salt and water
• Except for formed magnesium sulfate salt, group 2 formed sulfates tend to form insoluble layer on carbonate preventing further reaction
• Dilute hydrolylic acid reaction with group 2 forming soluble chloride salts
• Carbonate and nitrate decompose given off metal oxide
• Temperature at which thermal decomposition takes place increases down group 2
Uses of group 2 compounds: Limestone (calcium carbonate):
1- There are many types of limestone that provide useful rocks for building
2- Marble is another form of calcium carbonate used as a building material such as tiles
3- Calcium carbonate also used to make cement:
First step is roasting limestone in lime kiln
At high temp. in the kiln calcium carbonate decomposes to calcium oxide (quicklime) that is roasted and mixed with clay to make cement
Cement can also be mixed with sand and small pieces of rock to make concreter
4- Slaked lime (calcium hydroxide Ca(OH)2):
Used to raise pH of acidic soil because calcium hydroxide is basic it reacts with acids in the soil and neutralize them raising the pH of the soil
5- Magnesium:
a. Soft light metal
b. Magnesium metal can be used an easily-burned substance with a bright light in photographic flash bulbs.
c. Epsom salts (magnesium sulfate):
d. Relieves pain and muscle cramp
6- Group 2 salts and fireworks:
• Barium - Barium is used to create green colors in fireworks and it can also help stabilize other volatile elements.
• Calcium - Calcium is used to deepen firework colors. Calcium salts produce orange fireworks.
• Magnesium - Magnesium burns a very bright white, so it is used to add white sparks or improve the overall brilliance of a firework.
• Strontium - Strontium salts impart a red color to fireworks. Strontium compounds are also important for stabilizing fireworks mixtures.
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Collagen is the
most abundant insoluble protein in animals, it is found in the extracellular
space of connective tissue, it comprises three peptide chains that bundle
together forming the distinct triple left-handed helix shape of collagen. The
triple chain, Tropocollagen, is a supercoil with a diameter of 1.4nm and made
up of 3 helices, each helix comprises around 1000 amino acid residues.
The three amino acids characteristic in the
repeating units of collagen helix are glycine, proline, and hydroxyproline. The
triple-helix motif is Gly-Y-X, where Y can either be proline or hydroxyproline,
and X can be any other amino acid. Each collagen unit has 3.3 residues per turn
and 0.54nm distance per pitch. The three-stranded helices are held together by the
hydrogen bond between NH glycine hydrogen and C=O of the adjacent polypeptide. The
angle of C-N peptidyl-proline or peptidyl-hydroxyproline is fixed, which makes
the three peptide chains fold into a helix (Lodish H, 2000).
Cells and
tissues in mammals are supported by collagen network; there are at least 16
types of collagen, about 80 to 90% of our body consists of three common types
of collagen I, II and III collagen.
Type I collagen
mostly found in bone (main component of the organic part of bone), dermis,
tendon, ligaments and cornea. Type II collagen is found in cartilage, vitreous
body, nucleus pulposus, and type III collagen found in tissues of the skin,
vessel wall, reticular fibers of most tissues (lungs, liver, spleen, etc.)(Gelse, 2003).
It is hard to
study collagen metabolism; studies show that the triple-helical molecules are
extracted by secretory vesicles from the Golgi compartment into the extracellular
space. The triple helix is cleaved by proteases (N and C) according to the type
of the produced collagen, both proteases (N and C), are Zn dependent. The
process of cleavage requires the presence of copper and vitamin C as well, yet
all data suggests that it is hard to study collagen metabolism because it turns
over slowly (Gelse, 2003).
Aging decreases
the amount of collagen that reaches the extracellular space, In addition the degradation
of tropocollagen by extracellular proteases leaves behind N- and C- terminal
fragments that accelerate the breaking down of collagen by metalloproteinases
matrix (MMPs)(Rennie, 1999).
But can the oral
intake of collagen peptide restore body collagen?
Exploring the
extent of collagen consumption is essential to comprehend the possibilities of
collagen to reach the extracellular space when orally consumed.
The main
questions would be; does the collagen peptide consumed orally reaches skin and
bone? Does the digestion process affect the integrity of the collagen peptide?
Skin collagen degrades
by metalloproteinases matrix (MMPs), topically administration of collagen
peptide (CH) delays aging, and treats the skin. The benefit of ingestion collagen
peptide remains obscure, the clinical community agreed on the fact that
ingestion of collagen in its hydrolyzed form suppresses the MMP2 activities leading
to a reduction of wrinkles(Zague, 2011), still extensive
studies were needed to establish concrete results.
Studies
that investigated the integrity of the ingestion of peptide showed that collagen
hydrolysate can cross the intestinal barrier reaching blood circulation, and
becomes available for the metabolic process, and storage in the skin. In fact,
the ingestion of a rich collagen diet promotes skin elasticity, reduces pain
for people suffering from osteoarthritis, inhabit cardiovascular damage and
collagen driven from fish has potent anti-oxidative effect. Collagen hydrolysate
supplements proved to relieve joints pain due to heavy exercises in athletes.(Clark, 2008).
A double-blind
placebo-controlled trial conducted on 69 women, aged between 35 and 55, for 8
weeks, showed that the oral intake of collagen hydrolysate enhances the skin
elasticity, and acts as a skin moisturizer in the elderly women (Proksch, 2014).
An interesting study on rats showed that oral
intake of collagen peptide in the presence and absence of calcium diet, both
increase the bone mass in rats. The rates with high collagen intake exhibited
hypertrophy in kidneys, without undesirable effects. The study provides another
evidence on the benefit of collagen oral intake on reducing osteopenia that
occurs with aging. (Wu, 2004).
Why there are still
some concerns?
In
the manufacture of collagen, the heavy metal test allows levels not to exceed the
approved human consumption. The effect of long collagen consumption is not
completely investigated; the accumulation of heavy metals and contaminant
effect would be seen after a long time, where most studies were performed for
short periods.
Many other potential sources have been investigated, in
Gómez-Guillén review (Gómez-Guillén, 2011). The review is considered to be a useful source for
information on alternative sources.
A clear picture
of the effect of collagen intake can be driven from the Japanese diet, the
Japanese diet contains a large portion of collagen. But where collagen-rich diet is
absent, collagen supplements are a very useful source of collagen.
Till now
collagen peptide supplement proved to be of a great benefit as long as the quality
of the product is been monitored.
References
Buehler, M. (2006). Nature designs tough collagen:
explaining the nanostructure of collagen fibrils. Proceedings of the
National Academy of Sciences, 103(33), 12285-12290.
Clark, K. S. (2008). 24-Week study on the use of
collagen hydrolysate as a dietary supplement in athletes with
activity-related joint pain. Current medical research and opinion, 25(5),
1485-1496.
Gelse, K. P. (2003). Collagens—structure, function,
and biosynthesis. Advanced drug delivery, 55(12), 1531-1546.
Gómez-Guillén, M. G.-C. (2011). Functional and
bioactive properties of collagen and gelatin from alternative sources: A
review. Food hydrocolloids, 25(8), 1813-1827.
Lodish H, B. A. (2000). Collagen: The Fibrous
Proteins of the Matrix. In B. A. Lodish H, Molecular Cell Biology. 4th
edition. New York: W. H. Freeman. Retrieved from
https://www.ncbi.nlm.nih.gov/books/NBK21582/
Proksch, E. S. (2014). Oral intake of specific
bioactive collagen peptides reduces skin wrinkles and increases dermal matrix
synthesis. Skin pharmacology and physiology, 27(3), 113-119.
Rennie, M. J. (1999). Teasing out the truth about
collagen. The Journal of physiology, 521.
Wu, J. F. (2004). Assessment of effectiveness of
oral administration of collagen peptide on bone metabolism in growing and
mature rats. Journal of bone and mineral metabolism, 22(6), 547-553.
Zague, V. d.-S. (2011). Collagen hydrolysate intake
increases skin collagen expression and suppresses matrix metalloproteinase 2
activity. Journal of medicinal food, 14(6), 618-624.
Group 2 (alkaline earth metals) physical properties (Chapter 11-Part 2):
The reason behind naming group 2 alkaline earth metals is that they form alkaline solution when dissolve in water.
Metallic radius is half the distance between the nuclei in a giant metallic lattice.
Metallic radius increases down group 2 because the atomic number increases and extra level is added down the group
Group 2 have high electric conductivity and the thermal conductivity.
Group 2 melting point trend:
Melting points decrease down the group although some irregularities are seen.
The reason behind the low melting point of magnesium comparing to calcium is the arrangement of metallic lattice for both elements.
• Be 1544, 1560, 1018, hcp (face centered cubic) at RT
• Mg 922, 755, 705, hcp (hexagonal close packed) at RT
• Ca 940, 1114, 1063, fcc at RT
• Sr 900, 1050, 1030, fcc at RT
• Ba 635, 1000, 709, bcc (body center cubic) at RT
Calcium has fcc arrangement where magnesium has hcp crystal packing, the high ductility makes melting point of calcium higher than magnesium.
Density trend for group 2 elements:
Density increases down group 2 as atomic number increases.
Again, some irregularities in density are also seen, calcium has lower density than magnesium. Crystal lattice of calcium has 14 atoms where magnesium has 19 atoms in its lattice which makes density of calcium lower than magnisium.
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Ever wondered why the sky is blue?
The sun is a large shiny star that sends light to all surrounding space.
Light can travel in a vacuum, and it travels to earth.
So, if the sun is sending white light, why the sky appear blue!
The light is an electromagnetic spectrum, electromagnetic wave, each wave travels from the sun with a different wavelength and different frequency.
The light coming from the sun contains all types of electromagnetic spectrum, such as; microwaves, infrared light, ultraviolet light, X-rays, gamma-rays, and visible light.
White light is a mixture of wavelengths, of the visible portion, of the electromagnetic spectrum (visible spectrum).
We see all the rainbow colors mixed as white light, but if we passed light through a prism, we will see rainbow colors.
Each color we see comprise a certain amount of energy, has a certain wavelength, and definite frequency.
When white light falls on your red T-shirt, your T-shirt absorbs all colors except for red. Your T-shirt reflects the red color, and you see your T-shirt in red.
A similar thing happens in the sky. When the white color coming from the sun interact with the atmosphere, the air particles absorb all visible colors except for blue.
Air particles scatter the blue color in all directions, this is why we see the sky in blue, and we see the scattered blue color.
But why the clouds appear white?
Clouds are made of water vapor, water vapor consists of large water molecules that scatter all colors.
We see these colors mixed as a white color, and the clouds appear white. Water molecules are transparent, but they are so large that they scatter all visible spectrum and appear white.
So why clouds sometimes appear gray?
The scattered light from the white clouds scatter in all directions, but on a rainy day, the water molecules at the bottom of the cloud become so dense to allow the light to pass, where the top part of the cloud scatter light. The clouds become dark from the bottom, and light from the top, and we see them in gray.
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Periodicity of chemical properties (Chapter 10 - Part 4):
Going across a period the elements get more electronegative as electrons are more strongly attracted by the increasing positive nuclear charge.
2- The electronegativity and acidic/basic nature of the Period 3 oxides:
a. Na, Mg, and Al form an ionic bond with oxygen in their oxides forming a large lattice.
b. Silicon bond covalently with oxygen to form SiO2 that has large molecular lattice.
3- The high melting points of ionic oxides make them suitable to be used in:
a. magnesium oxide to line the inside of furnaces.
b. aluminum oxide and silicon dioxide are used to make ceramics, with giant covalent structures designed to withstand high temperatures and provide electrical insulation.
c. P, S and chlorine bond covalently with oxygen forming small molecules.
4- Chlorides of Period 3 elements:
Chlorine has electronegativity equal to -1 where the rest of period three elements form positive ions with chlorine because of lower electronegativity comparing to chlorine.
a. The first three elements chlorides dissolve in water forming hydrate ions.
b. AlCl3 dimerize into Al2Cl6 solid hydrate that breaks down releasing hydrogen ions that react with chlorine atoms forming white fumes.
c. Sulfur and phosphorus both form chlorides that hydrolyze forming hydrogen chloride fumes.
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Chemical properties periodicity in periodic table ( CH10 part 3)
Period 3 chemical properties
Reaction of period 3 elements with chlorine gas
Reaction of period 3 elements with water
Reaction of period 3 elements with oxygen
period 3 oxides
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