Chlorine and Iodine

• Chlorine and iodine belong to the halogen group of the periodic table - Group 17.

• Both elements possess seven valence electrons, which they attempt to fill by gaining one electron from reactions, forming a -1 ion.

• Chlorine (atomic number 17) and iodine (atomic number 53) have different physical states at room temperature due to the increase in molecular size and Vanderwaals forces, with chlorine being a yellow-green gas and iodine a grey solid.

• Chlorine is more reactive than iodine due to its higher electronegativity, resulting from its smaller atomic radius and stronger nuclear attraction on the outer shell electrons.

• In displacement reactions between halogens and halides, chlorine can displace iodide ions because of its higher reactivity, whereas iodine cannot displace chloride ions.

• Both chlorine and iodine form diatomic molecules (Cl2, I2) in their elemental states.

• They can form a number of compounds with metals and non-metals. With metals, they form salts (e.g., sodium chloride, sodium iodide), and with hydrogen they form acidic hydrogen halides (hydrochloric acid, hydroiodic acid).

• Iodine has special importance in the human body as it is an essential trace element needed for the synthesis of hormones in the thyroid gland. Lack of iodine in diet can lead to a disorder called goitre.

• Chlorine is commonly used as a disinfectant in pools and drinking water because of its ability to kill bacteria and other microorganisms.

• It’s important to remember to handle both elements with care in a laboratory setting. Chlorine is a highly toxic and corrosive gas, and iodine can be harmful in large amounts or prolonged exposure. Always follow safety precautions when working with these elements.