WHAT IS PERIODIC TABLE?
It is a tabular display of chemical elements, arranged in order of atomic number in rows so that elements with similar atomic structure and recurring chemical properties appear in vertical columns. The seven rows of the table are called a periodic table.
In the periodic table, chemical elements are present in rows horizontally in order of increasing atomic number and vertically according to the recurring properties of their atoms.
Metals are on the left side and non-metal are on the right side of the periodic table
In the periodic table of chemical elements, there is a group (also known as a family) is a column of elements. There are multiple ways of grouping the elements but they are commonly divided into metals, non-metals, metalloids. There are also more specific groups like alkali metals, transition metals, rare metals, alkaline earth, halogens, and noble gases.
The 18 vertical columns of the table are called Groups. The s-, p- and d-block elements of the periodic table are arranged into these columns or groups. Each group of elements having the same number of valence electrons. The Same group elements have similar properties and reactivity. These elements tend to show patterns in atomic radius, ionization energy, and electronegativity.
GROUP 2 OF THE PERIODIC TABLE
Group 2 elements are:
Group 2 elements are called alkaline metals because they form alkaline solutions, hydroxides, when reacting with water and their oxides are found in the earth’s crust.
- They have low electron affinity.
- Group 1 metals are less reactive than group 2 metals.
- Its valence shell contains 2 electrons
- They have low electronegativity
- Compounds of alkali metals are often insoluble in water
- Alkaline metals are usually Shiny, silvery.
- They have ions with a +2 charge.
- They are solid
- They are harder, denser, stronger
- They are found in the earth crust
|State at 20⁰||Solid|
|Density (g cm-3)||1.85|
|Relative atomic mass||9.012|
It is a rare element in-universe. Beryllium was discovered in 1798 by French chemist Nicolas-Louis Vauquelin. The name was derived from the Greek name beryl, ‘beryllo’. Friedrich Wohler at berlin in 1828 isolated the beryllium metal. Beryllium generally occurs in the earth’s crust to the extent of 0.0002 percent. Beryllium is a steel-gray metal. It is quite brittle. Its chemical properties resemble aluminum. Emerald is known to be a variety of beryl.
It has a close-packed hexagonal crystal structure.it has a very high melting point which makes beryllium metal the best heat dissipation characteristics per unit weight.it has a low coefficient of linear thermal expansion. These characteristics make unique stability under thermal loading. In the air, beryllium resists oxidation and corrosion.it is extracted by the mineral beryl.
While bonding with the other atoms, it has a very high ionization potential and strong polarization. Beryllium has a +2 oxidation state.it allows forming many covalent bonds.it dissolves in non- oxidizing acids. Binary compounds are formed by the combination of beryllium with non-metals such as Beryllium oxide (BeO). It is white solid and has a very high melting point. Emerald and aquamarine contain Beryllium.
- It is used to make semiconductor devices.
- It is useful in making radio equipment and engines.
- It is used in making windows for X-rays tubes.
- Useful for mirrors and camera shutters.
- It is fabricated into gyroscopes, computer parts, and accelerometers.
|Specific gravity||1.74 at 20,68|
|Thermal conductivity||156 W m-1K-1|
|Electrical conductivity||22.4 x 106 Sm-1|
It was first isolated in 1808 by Sir Humphrey Davy by the process of mercury evaporation from the magnesium amalgam which is made by the electrolyzing a mixture of moist magnesia and mercuric oxide. By heating, mercury was removed from the amalgam and leave the mercury metal. He isolated many other alkalies and alkali earth metals.
In June 1808 he described how he obtained magnesium by removing mercury. He observed that in the air the metal turned into white powder and gains weight, reacts with oxygen and returned to its oxide form.
In the earth’s crust, it is the eighth-most abundant element.it is found in more than 60 minerals.it is found in large deposits of dolomite, magnesite, brucite, and carnallite and in mineral water where magnesium is soluble.
Production of magnesium
The double carbonate of calcium and magnesium, dolomite is far more widely distributed and seawater provides an inexhaustible source of the chloride in the dilute form, while certain concentrated solutions of magnesium salts are present in the Dead sea.
There are two methods for the production of magnesium
- Electrolysis ( Dow process )
- Thermal reduction (Pidgeon process )
It consists of two steps
- The preparation of raw material contains magnesium chloride
- By the separation of magnesium chloride into magnesium metal and chlorine gas in electrolytic cells
MgCl2 Mg + Cl2
Magnesium produced on the power consumption of 12 – 18 kilowatt-hour per kilogram.in the dehydration process, chlorine can also be reused.
In the thermal production of magnesium, the endothermic reaction takes place. On the high temperature, the reduction of oxides with silicon, frequently ferrosilicon alloy is provided to obtain metal. Carbon is also carried out in this process
2MgO + Si + 2CaO 2Mg + Ca2SiO4
MgO + Ca Mg + CaO
After extraction, crude magnesium is transported to the shops to remove impurities.
Characteristics and uses
- Magnesium powder is an explosive hazard.
- It is widely used in the manufacturing of mobiles, laptops, cameras and other electronic components.
- It has good high-temperature mechanical properties and high corrosion resistance.
- It is used in the manufacturing of aircraft, car engines and missile construction.
|Melting point||842 (1548)|
|Boiling point||1484 (2703|
|Specific gravity||1.55 ( 20|
For centuries calcium oxide is used to make plaster and mortar, obtained by heating limestone.in 1808 Humphrey Davy tried to reduce moist lime by electrolysis but he was not successful. Then he tried the mixture of mercury oxide and lime, this produced an amalgam of calcium and mercury. Then Davy tried using more lime in the mixture and produced more of the amalgam from which he distilled off the mercury and leaving just calcium. The word calcium derives from the Latin word for lime ‘calx’.
Production of calcium
- The reaction of calcium chloride with sodium lead alloy
- By the electrolysis of molten salt of calcium chloride
- Reduction of calcium compounds by use of Si, Al, Ti, Be
Facts about the calcium
- Calcium is not found free. It the 5th most abundant element in the earth’s crust. Calcium is also abundant on the Moon.
- Calcium is the most important nutrition for plants and animals. It also exists in the human body, found mainly in bones and teeth.
- Snails and shellfish use calcium in the form of calcium carbonate to build their shells.
- Dairy products and grains are the primary sources of dietary calcium.
- Later the Egypt’s pyramid blocks were built using limestone. The blocks were held together with gypsum and lime-based mortar.
- Calcium is used in the production process of other metals like uranium and thorium
- Calcium is also used in vacuum tubes.
- It can be alloyed with aluminum, copper, lead, magnesium, and beryllium.
- Used in cement and concrete
- It is used to remove sulfur, oxygen, and carbon from alloys.
- It is used in the making of chalks and statues.
- Used in the making of cheese.
It was discovered by the Irish chemist Adair Crawford in 1790. It is found from the lead mine near village Strontian in Scotland. Strontium is the 15th most abundant element on the earth’s crust. In 1808 Humphrey Davy isolated the strontium metal, who electrolyzed a mixture of the moist hydroxide or chloride with mercuric oxide, using a cathode oxide and then evaporated the mercury from the resultant amalgam. Davy built a very large battery consists of 600 plates from which he passes the electricity through salts breaking them down to isolate a new element. He made a paste of magnesium oxide and strontium sulfate and made a depression in a paste to place mercury metal as an electrode. Platinum is also used as an electrode at a mercury electrode, strontium mercury amalgam is formed when the electricity passes through the paste. By heating mercury removed from the amalgam and leave the strontium metal.
Strontium isotopes are considered non-toxic. Strontium is a mixture of 4 stable isotopes. It a silvery metal with a pale yellow tint. It is harder than barium and softer than calcium. When strontium reacts with water it produces strontium hydroxide and hydrogen gas. It occurs naturally in compounds and other elements that’s why it has extreme reactivity with oxygen and air.
- Strontium is used in the manufacture of color television picture tubes.
- It is used in the fireworks and signal flares.
- Its carbonates are used to make a certain type of glass.
- It plays a great role in biology. Strontium deposited in human bones and attaches on the surface of the bones, it can replace the calcium and lead to the growing problems.
- Used in toothpaste to reduce sensitivity
- It can increase the risk of cardiovascular problems
- It is used in refining zinc and also used to produce ceramic magnets.
In 1774, a Swedish chemist Carl Wilhelm Scheele discovered a new base (BaO).In pyrolusite, BaO considered a minor component and he prepared the crystals of barium sulfate from that base. Then he sent the crystals of barium sulfate to John Gottlieb Gahn. After a month, he founded that mineral barite is composed of barium sulfate BaSO4. In the early 17th century, the crystalline form of barite found near Italy. After heating with charcoal it became an impure barium sulfide. It is an unusual discovery of Bologna stone, nobody suspected that there was a new element to be discovered.
In 1808, for the first time, Sir Humphrey Davy isolated the Barium metal. By electrolysis, he decomposed the barium sulfate. The name Barium is given from the Greek word Barys means heavy. Barium is found 0.045% in the earth’s crust and 13 ug/L in seawater.
Barium is a very reactive metallic element. It resembles calcium. It is a silvery-white metal. When it cuts, it quickly turns into a black color due to the formation of barium oxide. Barium is commonly found as barite and witherite. It has a good conductivity.it is a mixture of 6 stable isotopes. Barium compounds that are soluble having a very poisonous property.
- Barium is used in the manufacturing of rubber, vacuum tubes, and pyrotechnics.
- It is used as a weighting compound in the manufacturing of glass, paints, and pigments.
- It is used as a deoxidizer in copper refining.
- In X-rays, it is used as an opaque medium to examine the gastrointestinal tract.
- It is used in capacitors
- Used in non-linear optical applications
|Atomic weight||(226) no stable isotopes|
|Electron configuration||(Rn) 7s2|
|Melting point||700oC, 973K|
|Boiling point||1500oC, 1773K|
|Atomic radius||215 pm|
|Specific gravity||5.5 g/cm3|
In 1898, radium was discovered by Pierre Curie, Marie Curie, and an assistant G. Belmont. Radium compound extracted from the uraninite, he published the discovery at the French Academy of Sciences. By electrolysis of radium chloride, radium was isolated in its metallic state by Marie Curie in 1910. Isotopes of radium have half-lives much shorter than the age of the earth. According to the geological survey, radium would have disappeared a long time ago. Thus it is found in unrefined uranium.
Radium is silvery-white metal. When exposed to air it blackens itself. It is volatile than barium. It has very high radiological hazards.it emits alpha, beta and gamma rays. It is a member of uranium decay series.
- Alpha particles that are emitted by radium were used to initiate nuclear reactions.
- It has a major role in medicines, particularly in the treatment of cancer by the radiation of gamma rays
- Radium was used for the production of luminous paints but now it is not safe to use these paints because of its hazard property.
- In commercially, it is used for the production of toothpaste, hair creams
- It is also used in the production of food items due to its curing power.