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Silver

palladium – silver – cadmium Cu Ag Au     Full table
General
Name, Symbol, Number	silver, Ag, 47
Chemical series	Transition metals
Group, Period, Block	11, 5 , d
Density, Hardness	10490 kg/m3, 2.5
Appearance	Lustrous white metal
Atomic properties
Atomic weight	107.8683 amu
Atomic radius (calc.)	160 (165) pm
Covalent radius	153 pm
van der Waals radius	172 pm
Electron configuration	[Kr]4d4d10 5s1
e- 's per energy level	2, 8, 18, 18, 1
Oxidation state (Oxide)	1 (amphoteric)
Crystal structure	Face centered cubic
Physical properties
State of matter	Solid (__)
Melting point	1234.93 K (1763.2 °F)
Boiling point	2435 K (3924 °F)
Molar volume	10.27 ×10;10-6 m3/mol
Heat of vaporization	250 .58 kJ/mol
Heat of fusion	11.3 kJ/mol
Vapor pressure	0.34 Pa at 1234 K
Speed of sound	2600 m/s at 293.15 K
Miscellaneous
Electronegativity	1.93 (Pauling scale)
Specific heat capacity	232 J/(kg*K)
Electrical conductivity	63 106/m ohm
Thermal conductivity	429 W/(m*K)
1st ionization potential	731.0 kJ/mol
2nd ionization potential	2070 kJ/mol
3rd ionization potential	3361 kJ/mol
Most Stable Isotopes
iso NA half-life DM DE MeV DP 107Ag 51.839% Ag is stable with 60 neutrons 108Agm {syn.} 418 y ε IT 2.027 0.109 108Pd   109Ag 48.161% Ag is stable with 62 neutrons
SI units & STP are used except where noted.

Silver is a chemical element in the periodic table that has the symbol Ag and atomic number 47. A soft white lustrous transition metal, silver has the highest electrical and thermal conductivity of any metal and occurs in minerals and in free form. This metal is used in coins, jewelry, tableware and photography.

Table of contents

1 Notable characteristics 2 Applications 3 History 4 Occurrence 5 Isotopes 6 Precautions and health effects 7 Reference 8 External links

Notable characteristics

Pure silver also has the highest thermal conductivity, whitest color, the highest optical reflectivity (although it is a poor reflector of ultraviolet), and the lowest contact resistance of any metal. Silver halides are photosensitive and are remarkable for the effect of light upon them. This metal is stable in pure air and water, but does tarnish when it is exposed to ozone, hydrogen sulfide, or air with sulfur in it. The most common oxidation states of silver are +1 and +2.

Applications

• Electrical and electronic products, which need silver's superior conductivity, even when tarnished. For example, printed circuits are made using silver paints, and computer keyboards use silver electrical contacts.
• Mirrors which need silver's superior reflectivity for visible light are made with silver as the reflecting material. Common mirrors are backed with aluminium.
• Silver has been coined to produce money since 700 BC with the Lydians, in the form of electrum. Later, silver was refined and coined in its pure form. The words for "silver" and "money" are the same in at least 14 languages.
• The beauty of the metal is chosen for the manufacture of jewelry and silverware, and are traditionally made from the silver alloy known as Sterling silver, which is 92.5% silver.
• The malleability, non-toxicity and beauty of silver make it useful in dental alloys for fittings and fillings.
• Silver's catalytic properties make it ideal for use as a catalyst in oxidation reactions; for example, the production of formaldehyde from methanol and air by means of silver screens or crystallites containing a minimum 99.95 weight-percent silver.
• Used to make solder and brazing alloys, electrical contacts, and high capacity silver-zinc and silver-cadmium batteries.
• Silver sulphide, also known as Silver Whiskers, is formed when silver electrical contacts are used in an atmosphere rich in Hydrogen Sulphide.
• Silver fulminate is a powerful explosive.
• Silver chloride can be made transparent and is used as a cement for glass.
• Silver iodide has been used in attempts to seed clouds to produce rain.
• In legend, silver is traditionally seen as harmful to supernatural creatures like werewolves and vampires. The use of silver fashioned into bullets for firearms is a popular appllication.

Silver has been used for thousands of years as ornaments and utensils, for trade, and as the basis for many monetary systems. It was long considered the second most precious metal, second only to gold.

Associated with the moon, as well as with the sea and various lunar goddesses, the metal was referred to by alchemists by the name luna. The alchemical symbol for silver is a half-moon with the open part on the left.

The metal mercury was thought of as a kind of silver, though the two elements are chemically unrelated; its names hydrargyrum ("watery silver") and the English quicksilver attest to this.

In heraldry, the argent, in addition to being shown as silver (this has been shown at times with real silver in official representations), can also been shown as white. Occasionally, the word "silver" is used rather than argent; sometimes this is done across-the-board, sometimes to avoid repetition of the word "argent" in blazon.

Europeans found huge amount of silver in the New World in Zacatecas, Mexico and Potosí, which triggered a period of inflation in Europe.

The Rio de la Plata was named after silver (in Spanish, plata), and in turn lent the meaning of its name to Argentina.

Occurrence

This metal is also produced during the electrolytic refining of copper. Commercial grade fine silver is at least 99.9% pure silver and purities greater than 99.999% are available. Mexico is the largest silver producer. According to the Secretary of Economics of Mexico, it produced 2747 tons in 2000, about 15% of the annual production of the world.

Isotopes

Isotopes of silver range in atomic weight from 93.943 amu (Ag-94) to 123.929 amu (Ag-124). The primary decay mode before the most abundant stable isotope, Ag-107, is electron capture and the primary mode after is beta decay. The primary decay products before Ag-107 are palladium (element 46) isotopes and the primary products after are cadmium (element 48) isotopes.

The palladium isotope Pd-107 decays by beta emission to Ag-107 with a half-life of 6.5 million years. Iron meteorites are the only objects with a high enough Pd/Ag ratio to yield measurable variations in Ag-107 abundance. Radiogenic Ag-107 was first discovered in the Santa Clara meteorite in 1978. The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. Pd-107 versus Ag correlations observed in bodies, which have clearly been melted since the accretion of the solar system, must reflect the presence of live short-lived nuclides in the early solar system.

Precautions and health effects

Compounds containing silver can be absorbed into the circulatory system and become deposited in various body tissues leading to the condition called argyria which results in a permanent grayish pigmentation of the skin and mucous membranes. Although this condition does not harm a person's health, it is disfiguring.

This metal plays no natural biological role in humans.

The possible health effects of silver are a subject of dispute. Silver has germicidal effects and kills many microbial organisms in vitro without causing noticeable harm to more complex life-forms. Hippocrates, the father of modern medicine, wrote that silver had beneficial healing and anti-disease properties. Various kinds of silver compounds are sold as remedies for a variety of diseases. However, no clinical study has yet demonstrated a therapeutic use for silver as an antibiotic in vivo. Ingestion of silver compounds can lead to argyria.

Silver compounds are used to accelerate healing in burn victims. According to Dr. Robert O. Becker, they can promote the healing of bones as well.

Silver is used in along with copper as an agent to remove algae in swimming pools in the United States by use of electrolysis. Copper is active against algae while silver is active against bacteria primarily due to silver's activity in absorption of oxygen causing bacteria to oxidize on contact. Some swimming pools do not use silver due to staining problems so they instead used copper - zinc colloids instead.

Reference

• Los Alamos National Laboratory – Silver

• WebElements.com – Silver
• EnvironmentalChemistry.com – Silver

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