silicon (si)

                                                     SILICON

Silicon Image

 Atomic Number: 14

Symbol: Si

Atomic Weight: 28.0855

Discovery: Jons Jacob Berzelius 1824 (Sweden)

Electron Configuration: [Ne]3s²3p²

Word Origin: Latin: silicis, silex: flint

Element Classification: Semimetallic

Density (g/cc): 2.33

Melting Point (K): 1683

Boiling Point (K): 2628

Appearance: Amorphous form is brown powder; crystalline form has a gray

Atomic Radius (pm): 132

Atomic Volume (cc/mol): 12.1

Covalent Radius (pm): 111

Ionic Radius: 42 (+4e) 271 (-4e)

Specific Heat (@20°C J/g mol): 0.703

Fusion Heat (kJ/mol): 50.6

Evaporation Heat (kJ/mol): 383

Debye Temperature (K): 625.00

Pauling Negativity Number: 1.90

First Ionizing Energy (kJ/mol): 786.0

Oxidation States: 4, -4

Lattice Structure: Diagonal

Lattice Constant (Å): 5.430

Preparation: Silicon may be prepared by heating silica and carbon in an electric furnace, using carbon electrodes. Amorphous silicon may be prepared as a brown powder, which can then be melted or vaporized. The Czochralski process is used to produce single crystals of silicon for solid-state and semiconductor devices. Hyperpure silicon may be prepared by a vacuum float zone process and by thermal decompositions of ultra-pure trichlorosilane in an atmosphere of hydrogen.

Properties: The melting point of silicon is 1410°C, boiling point is 2355°C, specific gravity is 2.33 (25°C), with a valence of 4. Crystalline silicon has a metallic grayish color. Silicon is relatively inert, but it is attacked by dilute alkali and by halogens. Silicon transmits over 95% of all infrared wavelengths (1.3-6.7 mm).

Uses: Silicon is one of the most widely used elements. Silicon is important to plant and animal life. Diatoms extract silica from water to build their cell walls. Silica is found in plant ashes and in the human skeleton. Silicon is an important ingredient in steel. Silicon carbide is an important abrasive and is used in lasers to produce coherent light at 456.0 nm. Silicon doped with gallium, arsenic, boron, etc. is used to produce transistors, solar cells, rectifiers, and other important solid-state electronic devices. Silicones range from liquids to hard solids and have many useful properties, including use as adhesives, sealants, and insulators. Sand and clay are used to make building materials. Silica is used to make glass, which has many useful mechanical, electrical, optical, and thermal properties.

Sources: Silicon makes up 25.7% of the earth's crust, by weight, making it the second most abundant element (exceeded by oxygen). Silicon is found in the sun and stars. It is a principal component of the class of meteorites known as aerolites. Silicon is also a component of tektites, a natural glass of uncertain origin. Silicon is not found free in nature. It commonly occurs as the oxide and silicates, including sand, quartz, amethyst, agate, flint, jasper, opal, and citrine. Silicate minerals include granite, hornblende, feldspar, mica, clay, and asbestos.

Aluminium (Al)

                                             AIUMINUM OR ALUMINIUM

Aluminum or Aluminium Image

Atomic Number: 13

Symbol: Al

Atomic Weight: 26.981539

Discovery: Hans Christian Oersted (1825, Denmark), Wohler (1827)

Electron Configuration: [Ne] 3s2 3p1

Word Origin: Latin alumen: alum, an astringent and dyeing mordant

Note on Naming: Sir Humphry Davy proposed the name aluminum for the metal, however, the name aluminium was adopted to conform with the "ium" ending of most elements. This spelling is in use in most countries. Aluminium was also the spelling in the U.S. until 1925, when the American Chemical Society officially decided to use the name aluminum instead.

Element Classification: Metal

Density (g/cc): 2.6989

Appearance: soft, lightweight, silvery-white metal

Atomic Radius (pm): 143

Atomic Volume (cc/mol): 10.0

Covalent Radius (pm): 118

Ionic Radius: 51 (+3e)

Specific Heat (@20°C J/g mol): 0.900

Fusion Heat (kJ/mol): 10.75

Evaporation Heat (kJ/mol): 284.1

Debye Temperature (K): 394.00

Pauling Negativity Number: 1.61

First Ionizing Energy (kJ/mol): 577.2

Oxidation States: 3

Lattice Structure: Face-Centered Cubic

Lattice Constant (Å): 4.050

Properties: Aluminum has a melting point of 660.37°C, boiling point of 2467°C, specific gravity of 2.6989 (20°C), and valence of 3. Pure aluminum is a silvery-white metal. It is soft, light, relatively nontoxic, with a high thermal conductivity, and high corrosion resistance. It can be easily formed, machined, or cast. Aluminum is nonmagnetic and nonsparking. It is second among metals in terms of malleability and sixth in ductility. Aluminum coatings are highly reflective of both visible and radiant heat. The coatings form a thin layer of protective oxide and do not deteriorate like silver coatings.

Uses: Ancient Greeks and Romans used alum as an astringent, for medicinal purposes, and as a mordant in dyeing. It is used in kitchen utensils, exterior decorations, and thousands of industrial applications. Although the electrical conductivity of aluminum is only about 60% that of copper per area of cross section, aluminum is used in electrical transmission lines because of its light weight. The alloys of aluminum are used in the construction of aircraft and rockets. Reflective aluminum coatings are used for telescope mirrors, making decorative paper, packaging, and many other uses. Alumina is used in glassmaking and refractories. Synthetic ruby and sapphire have applications in producing coherent light for lasers.

Sources: Aluminum is the most abundant metal in the Earth's crust (8.1%), although it is not found free in nature. In 1886, Hall in the United States and Heroult in France discovered how to obtain aluminum metal from electrolysis of alumina dissolved in cryolite. Cryolite is an aluminum ore, although it is has been replaced for commercial aluminum purification by an artificial mixture of sodium, aluminum, and calcium fluorides. The Bayer process is commonly used to refine the impure hydrated oxide ore, bauxite, for use in the Hall-Heroult refining process. Aluminum also can be produced from clay, although this is not the most economically feasible method at present. In addition to cryolite and bauxite, aluminum is found in feldspars, granite, and many other common minerals. The oxide, alumina, occurs naturally as ruby, sapphire, emery, and corundum.

Magnesium (Mg)

                                            MAGNESIUM (Mg)

Magnesium Image

   

Magnesium

Atomic Number: 12

Symbol: Mg

Atomic Weight: 24.305

Discovery: Recognized as an element by Black 1775; Isolated by Sir Humphrey Davy 1808 (England)

Electron Configuration: [Ne] 3s²

Word Origin: Magnesia, a district in Thessaly, Greece

Atomic Weight: 24.305

Element Classification: alkaline earth metal

Density (g/cc): 1.738

Appearance: lightweight, malleable, silvery-white metal

Atomic Radius (pm): 160

Atomic Volume (cc/mol): 14.0

Covalent Radius (pm): 136

Ionic Radius: 66 (+2e)

Specific Heat (@20°C J/g mol): 1.025

Fusion Heat (kJ/mol): 9.20

Evaporation Heat (kJ/mol): 131.8

Debye Temperature (K): 318.00

Pauling Negativity Number: 1.31

First Ionizing Energy (kJ/mol): 737.3

Oxidation States: 2

Lattice Structure:Hexagonal

Lattice Constant (Å): 3.210

Lattice C/A Ratio: 1.624

Properties: Magnesium has a melting point of 648.8°C, boiling point of 1090°C, specific gravity of 1.738 (20°C), and valence of 2. Magnesium metal is light (one-third lighter than aluminum), silvery-white, and relatively tough. The metal tarnishes slightly in air. Finely divided magnesium ignites upon heating in air, burning with a bright white flame.

Uses: Magnesium is used in pyrotechnic and incendiary devices. It is alloyed with other metals to make them lighter and more easily welded, with applications in the aerospace industry. Magnesium is added to many propellents. It is used as a reducing agent in the preparation of uranium and other metals that are purified from their salts. Magnesite is used in refactories. Magnesium hydroxide (milk of magnesia), sulfate (Epsom salts), chloride, and citrate are used in medicine. Organic magnesium compounds have many uses. Magnesium is essential for plant and animal nutrition. Chlorophyll is a magnesium-centered porphyrin.

Sources: Magnesium is the 8th most  abundant element in the earth's crust. While it is not found free it nature, it is available in minerals including magnesite and dolomite. The metal may be obtained by electrolysis of fused magnesium chloride derived from brines and seawater.

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)

                        

Sodium (Na)

                                                         SODIUM

         Sodium Image

Sodium Atomic Number: 11
Sodium Symbol: Na
Sodium Atomic Weight: 22.989768
Electron Configuration: [Ne]3s¹
Sodium Word Origin: English soda and Medieval Latin sodanum: headache remedy; Latin natrium: sodium carbonate
Isotopes: Seven isotopes of sodium are known.
Element Classification: Alkali Metal
Discoverer: Sir Humphrey Davy
Discovery Date: 1807 (England)
Density (g/cc): 0.971
Appearance: soft, silvery-white metal
Atomic Radius (pm): 190
Atomic Volume (cc/mol): 23.7
Covalent Radius (pm): 154
Ionic Radius: 97 (+1e)
Specific Heat (@20°C J/g mol): 1.222
Fusion Heat (kJ/mol): 2.64
Evaporation Heat (kJ/mol): 97.9
Debye Temperature (K): 150.00
Pauling Negativity Number: 0.93
First Ionizing Energy (kJ/mol): 495.6
Oxidation States: 1 Lattice Structure: Body-Centered Cubic
Lattice Constant (Å): 4.230

Properties: Sodium has a melting point of 97.81 +/- 0.03°C, boiling point of 882.9°C, specific gravity of 0.971 (20°C), and a valence of 1. Sodium is a bright, silvery metal. It is soft and highly reactive. Sodium floats on water, which decomposes it to evolve hydrogen and form the hydroxide. Sodium may ignite spontaneously on water. It does not usually ignite in air at temperatures below 115°C.
Uses: Sodium chloride is important for animal nutrition. Sodium compounds are used in the glass, soap, paper, textile, chemical, petroleum, and metal industries. Metallic sodium is used in manufacturing of sodium peroxide, sodium cyanide, sodamide, and sodium hydride. Sodium is used in preparing tetraethyl lead. It is used in the reduction of organic esters and preparation of organic compounds. Sodium metal may be used to improve the structure of some alloys, to descale metal, and to purify molten metals. Sodium, as well as NaK, an alloy of sodium with potassium, are important heat transfer agents.
Sources: Sodium is relatively abundant in the sun and other stars. The D lines of sodium are prominent in the solar spectrum. Sodium is the sixth most abundant element on earth. It comprises approximately 2.6% of the earth's crust. Sodium is the most abundant of the alkali metals. The most common sodium compound is sodium chloride (salt). Sodium occurs in many minerals, such as cryolite, soda niter, zeolite, amphibole, and sodalite. Sodium is not found free in nature. It is obtained commercially by the electrolysis of dry fused sodium chloride.

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952)

 

Neon (Ne)

                                             NEON

Basic Information

Name: Neon
Symbol: Ne
Atomic Number: 10
Atomic Mass: 20.1797 amu
Melting Point: -248.6 °C (24.549994 K, -415.48 °F)
Boiling Point: -246.1 °C (27.049994 K, -410.98 °F)
Number of Protons/Electrons: 10
Number of Neutrons: 10
Classification: Noble Gas
Crystal Structure: Cubic
Density @ 293 K: 0.901 g/cm³
Color: colorless

Facts

Date of Discovery: 1898
Discoverer: Sir William Ramsay
Name Origin: Form the Greek word neon (new)
Uses: lighting
Obtained From: liquid air

Related Links

None available

General Properties

• Symbol: Ne 
• Atomic Number: 10 
• Atomic weight 20.1797 g/mol
• Electron Configuration: [He] 2s² 2p⁶
• Colorless and odorless gas 
• Melting point: 24.56 K 
• Boiling point: 27.07 K 
• Density: 0.0008999 g/cm³
• 3 Stable isotopes 
• Crystal Structure: Face Centered  
• Fourth most abundant element in universe 
• Rare on earth: 0.001818% atmosphere 
•  Ionization Energy: 21.565 eV 

Figure 1

History and Origin

The name for the element Neon is derived from the Greek word for new, “neos”.  Since neon and the other noble gases are highly unreactive and only found in trace amounts in the atmosphere, they were not discovered until the late nineteenth century. Neon was discovered in 1898 by English chemists Sir William Ramsay and Morris M. Travers, along with Krypton and Xenon. They accomplished the isolation of these inert gases by fractional distillation of air. Through a two step process of condensation then evaporation, they were able to trap other components of the air. Initially, the group 18 elements were considered to be inert gases, as they were highly unreactive with any other element. However, in 1962 compounds of Xenon and Krypton compounds were synthesized with Fluorine, disproving their inert quality. Therefore, these elements were renamed the noble gases.

Occurrence

Neon is the fourth most abundant element in the entire universe, behind hydrogen, helium and oxygen. However, it is considered very rare on Earth as it can mainly be found in the atmosphere, which consists only 0.001818% of Neon in volume. This is because it is highly inert, very light, and has high vapor pressure at low temperatures. These properties explain why smaller, warmer, and solid planets like Earth are less abundant in Neon. Although, small traces of Neon can be encountered in the Earth's crust and ocean. Its estimated abundance is 5×10^-3 mg/Kg and 1.2×10^-4 mg/L respectively. Neon is the second lightest noble gas and is a monatomic gas, therefore found as Ne and not Ne₂.   

Formation of Compounds and Isotopes

Neon is known to form a compound with fluoride and an unstable hydrate.  Also, the ions Ne⁺, (NeAr)⁺ , (NeH)⁺, (HeNe)⁺  are known from mass spectrometry studies. However, not much has been verified about successful synthesized compounds of Neon.

The standard atomic mass of Neon is 20.1797 u. Neon is known to have over nineteen different isotopes ranging from 16-34 in isotopic mass. However, neon only has three stable isotopes: ²⁰Ne, ²¹Ne, and ²²Ne. The most abundant of those stable isotopes (no t_1/2 or decay) is ²⁰Ne at about 90%.

²⁵₁₂Mg → ²¹₁₀Ne + ⁴₂He  

* (alpha decay with Mg-25 to form Ne-21)

Applications and Uses

Neon is most notable for its use in neon lighting and signs. These neon lights are made with filled glass or plastic tubes with Neon gas.  As electricity passes through these tubes, electric discharge produces high-energy electrons that hit the neon atoms changing their energy state, as photon of light is emitted. These glass tubings can be shaped and twisted to form various designs.

It is a common misconception that all “neon” lights are made entirely of neon, as they do not change colors. Tubes filled solely with the Ne (g) emit the bright orange-red color. The different colors of lights are made by mixing other noble gases and elements. Over 150 colors can be made. (Ex: Mercury emits a light blue color). Other commercial uses for Neon are in high-voltage indicators, TV tubes, lightning arresters, and helium-gas lasers. Also, liquid neon is used as an economical cryogenic refrigerant.

*(Lightning Arrestor in a telephone pole to limit power surges)

 Problems

1)      What is the electron configuration of Ne⁺?

2)      Describe the process of fractional distillation of air.

3)      Why is Neon not abundant on Earth?

4)      Can the inert gas Neon react to form a compound?

5)      What color is a “neon light” that is filled with Argon and phosphor?