An Untitled presentation on halogens.pptx

halogens

1. Halogens Group VIIA

2. P roperties in Common six elements all form diatomic molecules (H2, F2, Cl2, Br2, I2, and At2) all form negatively charged ions (H-, F-, Cl-, Br-, I-, and At- Astatine is ignored because it is radioactive salt formers none of the halogens can be found in nature in their elemental form. found as salts of the halide ions

3. The Halogens in their Elemental Form Fluorine (F2) highly toxic, colorless gas, is the most reactive element known so reactive it even forms compounds with Kr, Xe, and Rn attacks both glass and quartz difficult to find a container in which it can be stored powerful oxidizing agent handled in equipment built out of certain alloys of copper and nickel used in the manufacture of Teflon and freons

4. Chlorine (Cl2) highly toxic gas with a pale yellow-green color strong oxidizing agent used commercially as a bleaching agent and disinfectant used to make solvents such as: carbon tetrachloride (CCl4), chloroform (CHCl3), dichloroethylene (C2H2Cl2), and trichloroethylene (C2HCl3)

5. Bromine (Br2) reddish-orange liquid with an unpleasant, choking odor Name- Greek stem bromos, "stench." used to prepare flame retardants, fire-extinguishing agents, sedatives, antiknock agents for gasoline, and insecticides.

6. Iodine intensely colored solid with an almost metallic luster relatively volatile , and it sublimes when heated to form a violet-colored gas Used as disinfectant in "tincture of iodine." compounds are used as catalysts, drugs, and dyes Silver iodide (AgI) plays an important role in the photographic process and in attempts to make rain by seeding clouds. Iodide is also added to salt to protect against goiter, an iodine deficiency disease characterized by a swelling of the thyroid gland.

7. Common Properties regular increase in many of the properties of the halogens as we proceed down the column from fluorine to iodine, including: the melting point boiling point intensity of the color of the halogen the radius of the corresponding halide ion the density of the element

8. Common Properties regular decrease in the first ionization energy as we go down this column, therefore; F2 > Cl2 > Br2 > I2 oxidizing strength And I- > Br- > Cl- > F- reducing strength

9. Methods of Preparing the Halogens from their Halides by reacting a solution of the halide ion with any substance that is a stronger oxidizing agent 2 I-(aq) + Br2(aq) ----> I2(aq) + 2 Br-(aq) 2 Br-(aq) + Cl2(aq) ----> Br2(aq) + 2 Cl-(aq) To prepare Cl2, we need a particularly strong oxidizing agent, such as manganese dioxide (MnO2). 2 Cl-(aq) + MnO2(aq) + 4 H+(aq) ----> Cl2(aq) + Mn2+(aq) + 2 H2O(l)

10. The synthesis of fluorine escaped the efforts of chemists for almost 100 years. The best way of producing a strong reducing agent is to pass an electric current through a salt of the metal. Sodium, for example, can be prepared by the electrolysis of molten sodium chloride. electrolysis 2 NaCl(l) ----> 2 Na(s) + Cl2(g) In theory, the same process can be used to generate strong oxidizing agents, such as F2.