Question 1: Halogens are a group of elements found in Group 7 of the periodic table. They include fluorine, chlorine, bromine, iodine, and astatine. These elements are known for their high reactivity and ability to form salts with metals.

Answer: Halogens are reactive non-metals in Group 7 of the periodic table that form salts with metals.

Question 1: Define the term 'halogen' and name all the elements in Group 7.

Answer: A halogen is a reactive non-metal in Group 7 of the periodic table; the elements are fluorine, chlorine, bromine, iodine, and astatine.

Question 2: Explain why the reactivity of halogens decreases as you move down Group 7.

Answer: Reactivity decreases down Group 7 because the outer electrons are farther from the nucleus, making it harder for the atom to attract and gain electrons.

Question 3: Describe the trend in melting points of the halogens as you go down Group 7.

Answer: Melting points increase down the group due to larger atomic size and stronger van der Waals forces between molecules.

Question 1: Calculate the number of electrons gained by a chlorine atom during a reaction, given that it gains one electron to form chloride ion.

Answer: 1 electron

Question 2: If the atomic mass of iodine is approximately 127 g/mol, how many atoms are in 1 gram of iodine?

Answer: Approximately 4.72 x 10^21 atoms

Question 1: Describe a simple experiment to test the reactivity of chlorine with a metal such as iron. Include safety precautions.

Answer: Add a small piece of iron to a solution of chlorine gas or a chlorine-containing compound in a well-ventilated area with proper protective equipment. Observe the formation of iron chloride. Ensure proper ventilation, wear gloves and eye protection to prevent inhalation and contact.

Question 1: A sample of bromine has a melting point of -7.2°C, and a sample of iodine melts at 113.7°C. Explain why the melting points differ significantly.

Answer: Bromine has weaker van der Waals forces than iodine due to its smaller atomic size, resulting in a lower melting point.

Question 2: A scientist observes that fluorine reacts vigorously with hydrogen to produce hydrogen fluoride. Based on this information, predict whether fluorine is more or less reactive than iodine and justify your answer.

Answer: Fluorine is more reactive than iodine because it has a higher tendency to gain electrons, and its small atomic size makes it more effective at attracting electrons.

Question 1: Explain how chlorine is used in water treatment and what safety considerations must be taken.

Answer: Chlorine is used to disinfect water by killing bacteria and other pathogens. Safety precautions include proper handling, avoiding inhalation of chlorine gas, and ensuring adequate ventilation to prevent toxic exposure.

Question 2: Identify one modern technological application of halogens and briefly describe its importance.

Answer: Halogens like fluorine are used in the production of Teflon (PTFE) for non-stick cookware, which is important for its chemical resistance and safety in cooking.