The document summarizes the properties of the halogens. It describes that the six halogens - fluorine, chlorine, bromine, iodine and astatine - all form diatomic molecules and negatively charged ions. They are salt formers and are not found in their elemental form in nature. The document then discusses the specific properties of each halogen in their elemental form and how they are prepared from their halides. It also notes that properties regularly increase or decrease going down the group.

1. Halogens
Group VIIA

2. Properties 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:
1. carbon tetrachloride (CCl4),
2. chloroform (CHCl3),
3. dichloroethylene (C2H2Cl2), and
4. 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.