Caesium (55)

Caesium is known as cesium in the USA.

The metal is characterised by a spectrum containing two bright lines in the blue (accounting for its name). It is silvery gold, soft, and ductile. It is the most electropositive and most alkaline element. Caesium, gallium, and mercury are the only three metals that are liquid at or around room temperature. Caesium reacts explosively with cold water, and reacts with ice at temperatures above -116°C. Caesium hydroxide is a strong base and attacks glass.

•Name: Caesium
•Symbol: Cs
•Atomic number: 55
•Atomic weight: 132.9054519 (2) 
•Standard state: solid at 298 K (but melts only slightly above this temperature)
•CAS Registry ID: 7440-46-2
•Group in periodic table: 1
•Group name: Alkali metal
•Period in periodic table: 6 
•Block in periodic table: s-block
•Color: silvery gold
•Classification: Metallic

Historical information
Caesium (cesium in USA) was discovered spectroscopically by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff in 1860 in samples of mineral water from Durkheim. Origin of name: from the Latin word "caesius" meaning "sky blue" or "heavenly blue". Their identification was based upon two bright blue lines in the spectrum. The name caesium (from the Latin "caesius" - heavenly blue) was coined for its bright blue spectroscopic lines.

Caesium salts were isolated by Bunsen by precipitation from these spring waters - along with salts of other Group 1 elements. He was able to separate them and isolated the chloride and the carbonate. He was unable to isolate caesium metal, this wasachieved by Setterberg.

Physical properties 
•Melting point: 301.59 [or 28.44 °C (83.19 °F)] K
•Boiling point: 944 [or 671 °C (1240 °F)] K
•Density of solid: 1879 kg m-3

Orbital properties
•Ground state electron configuration: [Xe].6s1
•Shell structure: 2.8.18.18.8.1
•Term symbol: 2S1/2

Isolation
Caesium (cesium in USA) would not normally be made in the laboratory as it is available commercially. All syntheses require an electrolytic step as it is so difficult to add an electron to the poorly electronegative caesium ion Cs+. 

Caesium is not made by the same method as sodium as might have been expected. This is because the caesium metal, once formed by electrolysis of liquid caesium chloride (CsCl), is too soluble in the molten salt.

cathode: Cs+(l) + e- → Cs (l) 

anode: Cl-(l) → 1/2Cl2 (g) + e-

Instead, it is made by the reaction of metallic sodium with hot molten caesium chloride.

Na + CsCl ⇌ Cs + NaCl

This is an equilbrium reaction and under these conditions the caesium is highly volatile and removed from the system in a form relatively free from sodium impurities, allowing the reaction to proceed. It can be purified by distillation.

 

Xenon (54)

Xenon is a "noble" or, more accurately, "inert" gas present in the atmosphere to a small extent. Xenon is present in the Martian atmosphere to the extent of about 0.08 ppm. Before 1962, it was generally assumed that xenon and other noble gases were unable to form compounds. Among the compounds of xenon now reported are xenon hydrate, sodium perxenate, xenon deuterate, difluoride, tetrafluoride, hexafluoride, and XePtF6 and XeRhF6. The highly explosive xenon trioxide, XeO3, is known.

Metallic xenon is produced by applying several hundred kilobars of pressure. Xenon in a vacuum tube produces a blue glow when excited by an electrical discharge and finds use in strobe lamps. It is an odourless, colourless, inert gas.

•Name: Xenon
•Symbol: Xe
•Atomic number: 54
•Atomic weight: 131.293 (6) [see note g 
•Standard state: gas at 298 K
•CAS Registry ID: 7440-63-3
•Group in periodic table: 18
•Group name: Noble gas
•Period in periodic table: 5 
•Block in periodic table: p-block
•Colour: colorless
•Classification: Non-metallic

Historical information
Xenon was discovered by Sir William Ramsay and Morris W. Travers at 1898 in England, in the residue left after evaporating liquid air components. Origin of name: from the Greek word "xenos" meaning "stranger". Krypton and neon had been discovered by the same methods by the same workers only weeks earlier. They had to work with huge volumes of air to produce just a little xenon since it turned out that xenon is only present to the extent of about 0.087 ppm in the atmosphere.

Physical properties 
•Melting point: 161.4 [or -111.7 °C (-169.1 °F)] K
•Boiling point: 165.1 [or -108 °C (-162 °F)] K
•Density of solid: 3640 kg m-3

Orbital properties
•Ground state electron configuration: [Kr].4d10.5s2.5p6
•Shell structure: 2.8.18.18.8
•Term symbol: 1S0

Isolation
Xenon is present to a small extent in the atmosphere (less than 1 ppm by volume) and is obtained as a byproduct from the liquefaction and separation of air. This would not normally be carried out in the laboratory and xenon is available commercially in cylinders at high pressure.

 

Iodine (53)

Iodine is a bluish-black, lustrous solid. It volatilises at ambient temperatures into a pretty blue-violet gas with an irritating odour.

It forms compounds with most elements, but is less reactive than the other halogens, which displace it from iodides. Iodine exhibits some metallic-like properties. It dissolves readily in chloroform, carbon tetrachloride, or carbon disulphide to form beautiful purple solutions. It is only slightly soluble in water. Iodine compounds are important in organic chemistry and very useful in medicine and photography. Lack of iodine is the cause of goiter (Derbyshire neck). The deep blue colour with starch solution is characteristic of the free element. It is assimilated by seaweeds from which it may be recovered, and is found in Chilean saltpetre, caliche, old salt brines, and salt wells.

Nitrogen triiodide is dangerously percussion sensitive (tap it - it goes BOOM!). Improperly done, this reaction is dangerous! 

•Name: Iodine
•Symbol: I
•Atomic number: 53
•Atomic weight: 126.90447 (3) 
•Standard state: solid at 298 K
•CAS Registry ID: 7553-56-2
•Group in periodic table: 17
•Group name: Halogen
•Period in periodic table: 5 
•Block in periodic table: p-block
•Color: violet-dark grey, lustrous
•Classification: Non-metallic

Historical information
Origin of name: from the Greek word "iodes" meaning "violet". Iodine was discovered by Bernard Courtois at 1811 in France. He isolated iodine from treating seaweed ash with sulphuric acid (H2SO4) while recovering sodium and potassium compounds.

Physical properties 
•Melting point: 386.85 [or 113.7 °C (236.66 °F)] K
•Boiling point: 457.4 [or 184.3 °C (363.7 °F)] K
•Density of solid: 4940 kg m-3

Orbital properties
•Ground state electron configuration: [Kr].4d10.5s2.5p5
•Shell structure: 2.8.18.18.7
•Term symbol: 2P3/2

Isolation
Iodine is available commercially so it is not normally necessary to make it in the laboratory. Iodine occurs in seawater but in much smaller quantities than chloride or bromide. As for bromine, with suitable sources of brine, it is recovered commercially through the treatment of brine with chlorine gas and flushing through with air. In this treatment, iodide is oxidized to iodine by the chlorine gas. 

2I- + Cl2 → 2Cl- + I2

Small amounts of iodine can be made through the reaction of solid sodium iodide, NaI, with concentrated sulphuric acid, H2SO4. The first stage is formation of HI, which is a gas, but under the reaction conditions some of the HI is oxidized by further H2SO4 to form iodine and sulphur dioxide.

NaI (s) + H2SO4 (l) → HI (g) + NaHSO4 (s)

2HI (g) + H2SO4 (l) → I2 (g) + SO2 (g) 2H2O

Fun Facts at a Glance: 

1.The name for iodine comes from the Greek word iodes, which means violet. Iodine gas is violet-colored.
2.Many isotopes of iodine are known. All of them are radioactive except for I-127.
3.Solid iodine is blue-black in color and shiny. At ordinary temperatures and pressures, iodine sublimates into its gas, so the liquid form is not seen.
4.Iodine is a halogen, which is a type of non-metal. Iodine possesses some characteristics of metals, too.
5.The thyroid gland uses iodine to make the hormones thyroxine and triiodotyronine. Insufficient iodine leads to development of a goiter, which is a swelling of the thyroid gland. Iodine deficiency is believed to be the leading preventable cause of mental retardation. Excessive iodine symptoms are similar to those of iodine insufficiency. Iodine toxicity is more severe if a person has a selenium deficiency.
6.Iodine occurs in compounds and as the diatomic molecule I2.
7.Iodine is used extensively in medicine. However, some people develop a chemical sensitivity to iodine. Sensitive individuals may develop a rash when swabbed with tincture of iodine. In rare cases, anaphylactic shock has resulted from medical exposure to iodine.
8.Natural food sources of iodine are seafood, kelp and plants grown in iodine-rich soil. Potassium iodide often is added to table salt to produce iodized salt.
9.The atomic number of iodine is 53, meaning all atoms of iodine possess 53 protons.
10.Commercially, iodine is mined in Chile and extracted from iodine-rich brines, notably from the oilfields in the US and Japan

 

Tellurium (52)

Crystalline tellurium has a silvery-white appearance, and exhibits a metallic lustre when pure. It is brittle and easily pulverised. Tellurium is a p-type semiconductor, and shows varying conductivity with crystal alignment. Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements.

Humans exposed to as little as 0.01 mg m-3 in air, or less, develop "tellurium breath", which has a garlic-like odour.

•Name: Tellurium
•Symbol: Te
•Atomic number: 52
•Atomic weight: 127.60 (3) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 13494-80-9
•Group in periodic table: 16
•Group name: Chalcogen
•Period in periodic table: 5 
•Block in periodic table: p-block
•Color: silvery lustrous grey
•Classification: Semi-metallic

Historical information
Tellurium was discovered by Franz Joseph Muller von Reichstein at 1783 in Romania. Origin of name: from the Latin word "tellus" meaning "earth" (note: tellus and terra were both Latin words for 'earth'. Tellus was a goddess of the earth, and Terra Mater was the Mother Earth). Tellurium was discovered in gold ores by Franz Joseph Mδller von Reichenstein, the chief inspector of mines in Trannsylvania in 1782. However tellurium was named by M. Klaproth, who isolated it in 1798, after he continued Mδller von Reichenstein's work.

Physical properties 
•Melting point: 722.66 [or 449.51 °C (841.12 °F)] K
•Boiling point: 1261 [or 988 °C (1810 °F)] K
•Density of solid: 6240 kg m-3

Orbital properties
•Ground state electron configuration: [Kr].4d10.5s2.5p4
•Shell structure: 2.8.18.18.6
•Term symbol: 3P2

Isolation
It is not usually necessary to make tellurium in the laboratory as it is commercially available. While there are some tellurium ores, most tellurium is made as a byproduct of copper refining. Extraction is complex since the method emplyed will depend upon what other compounds or elements are present. The first step usually involves an oxidation in the presence of sodium carbonate (soda ash).

Cu2Te + Na2CO3 + 2O2 → 2CuO + Na2TeO3 + CO2

The tellurite Na2TeO3 is acidified with sulphuric acid and the tellurium precipitates out as the dioxide (leaving and selenous acid, H2SeO3, in solution). Tellurium is liberated from the dioxide by dissolving in sodium hydroxide, NaOH, and electroytic reduction.