Antimony (51)

Metallic antimony is an extremely brittle metal of a flaky, crystalline texture. It is bluish white and has a metallic luster. It is not acted on by air at room temperature, but burns brilliantly when heated with the formation of white fumes. It is a poor conductor of heat and electricity.

Antimony and its compounds are toxic. It is found mostly with other minerals and in stibnite.

•Name: Antimony
•Symbol: Sb
•Atomic number: 51
•Atomic weight: 121.760
•Standard state: solid at 298 K
•CAS Registry ID: 7440-36-0
•Group in periodic table: 15
•Group name: Pnictogen
•Period in periodic table: 5
•Block in periodic table: p-block
•Color: silvery lustrous grey
•Classification: Semi-metallic

Historical information

Antimony was discovered by Known since ancient times at no data in not known. Origin of name is from the Greek words "anti + monos" meaning "not alone" (the origin of the symbol Sb comes from the Latin word "stibium"). Antimony was recognized in compounds by the ancients and was known as a metal at the beginning of the 17th century and possibly much earlier. Its most important mineral is stibnite, a mineral which formed the basis of black eye makeup in Biblical times. Antimony was sometimes confused with lead in those times. It seems not to be clear who first recognized antimony as an element but the French chemist Nicolas Lémery conducted much of the earlier studies on antimony chemistry.

Antimony is one of the elements which has an alchemical symbol, which looks like an upside down 'female' symbol. Alchemy is an ancient pursuit concerned with, for instance, the transformation of other metals into gold.

Physical properties

•Melting point: 903.78 [or 630.63 °C (1167.13 °F)] K
•Boiling point: 1860 [or 1587 °C (2889 °F)] K
•Density of solid: 6697 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d10.5s2.5p3
•Shell structure: 2.8.18.18.5
•Term symbol: 4S3/2

Isolation

It is not usually necessary to make antimony in the laboratory as it is commercially available. Antimony is found in nature in a number of minerals including stibnite (Sb2S3) and ullmanite (NiSbS). Small amounts of native antimony have been found. Some ores are treatable under reducing conditions to form Sb2S3. The sulfide is removed to leave elemental antimony with scrap iron.

Sb2S3 + 3Fe → 2Sb + 3FeS

In another process, some ores can be heated to evolve the oxide Sb2O3 and this in turn can be reduced by charcoal in the presence of sodium sulphate, to ensure mixing, to form elemental antimony.

2Sb2O3 +3C → 4Sb + 3CO2

Tin (50)

Ordinary tin is a silvery-white metal, is malleable, somewhat ductile, and has a highly crystalline structure. Due to the breaking of these crystals, a "tin cry" is heard when a bar is bent. The element has two allotropic forms. On warming, grey (or α-tin, alpha) tin (with a cubic structure), changes at 13.2°C into white (β-tin, beta), which is the ordinary form of the metal. White tin has a tetragonal structure. When tin is cooled below 13.2°C, it changes slowly from white to grey. This change is affected by impurities such as aluminum and zinc, and can be prevented by small additions of antimony or bismuth. The conversion was first noted as growths on organ pipes in European cathedrals, where it was thought to be the devils work (wasn't everything back then?). This conversion was also speculated to be caused microorganisms and was called "tin plague" or "tin disease".

Tin resists distilled, sea, and soft tap water, but is attacked by strong acids, alkalis, and acid salts. Oxygen in solution accelerates the attack. When heated in air, tin forms SnO2. It is, or was, used to plate steel, making "tin cans". Tin is used as one component in bell metals.

•Name: Tin
•Symbol: Sn
•Atomic number: 50
•Atomic weight: 118.710 (7) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-31-5
•Group in periodic table: 14
•Group name: (none)
•Period in periodic table: 5
•Block in periodic table: p-block
•Color: silvery lustrous grey
•Classification: Metallic

Historical information
Origin of name: from the Anglo-Saxon word "tin" (the origin of the symbol Sn comes from the Latin word "stannum" meaning "tin"). Tin was known to the ancients and is mentioned in the Old Testament. Early metal workers found it too soft for most purposes but mixed with copper it gives the alloy bronze, of Bronze Age fame.

Tin is one of the elements which has an alchemical symbol, which looks almost like a trident.

Physical properties
•Melting point: 505.08 [or 231.93 °C (449.47 °F)] K
•Boiling point: 2875 [or 2602 °C (4716 °F)] K
•Density of solid: 7310 kg m-3

Orbital properties
•Ground state electron configuration: [Kr].4d10.5s2.5p2
•Shell structure: 2.8.18.18.4
•Term symbol: 3P0

Isolation
There is normally little need to isolate tin metal in the laboratory as it is readily available commercially. Tin is commonly available as the mineral cassiterite, SnO2. Reduction of this dioxide with burning coal results in tin metal and was probably how tin was made by the ancients.

SnO2 + 2C → Sn + 2CO