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
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
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