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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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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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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Physical properties periodicity in periodic table (CH10 Part2) Periodic patterns of melting points and electrical conductivity Periodic patterns of first ionization energies Why silicon has highest melting point in period no. 3? Why aluminum has first ionization energy lower than magnesium? Why phosphorous has higher first ionization energy higher than sulfur? Visit us on: https://brightmindschemistry.blogspot.com https://chemistrybrightminds.wordpress.com/ https://brighteningmind.wixsite.com/channel https://www.facebook.com/BrightMinds
Physical properties periodicity in periodic table CH10 Part1
Atomic radius decreases a cross period and increases down the group
Ionic radius reduces for metals across period but increases for non-metals a cross period
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Rate of reaction
Effect of temperature and catalyst on rate of reaction
Type of catalysts
Biological catalysts: Enzymes
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Reaction Kinetics
Collision theory
Activation energy
The effect of concentration on rate of reaction
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Equilibria in gas reactions: the equilibrium constant Kp (Chapter 8 part 3)
Equilibrium expressions involving partial pressures Haber process in synthesis of ammonia and reaction equilibria synthesis of sulfuric acid and reaction equilibria
White light produces a continuous spectrum when passes through a prism.
If a cold gas tube placed in front of the source of the photons the gas atoms absorb energy to move electrons to an excited state and the produced is the absorption spectrum.
When the gas cools down electrons return to ground state and atom emits or release the emission spectrum or energy they gained before.
Each element has its specific fingerprint line-spectrum.
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Atomic radius is half the distance between two nuclei (r=d/2)
The atomic radius decreases across a period from left to right
The atomic radius increases down a group due to the increase in the number of levels
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Reversible reactions and equilibrium Le Chatelier’s principle Characteristic of equilibrium Factors affect position of equilibrium: Temperature, Concentration and pressure Exercises on the factors that can shift position of equilibrium Catalysts have no effect on position of equilibrium
