Phosgene was used as a chemical weapon during World War I. Despite the name, phosgene molecules contain no atoms of phosphorus. Instead, they contain atoms of carbon and the group 16 element in the second row of the periodic table and the group 17 element in the third row. What are the identities and atomic numbers of the two elements?
The correct answer and explanation is:
Correct Answer:
The two elements in phosgene are oxygen (O) with atomic number 8, and chlorine (Cl) with atomic number 17.
Explanation:
Phosgene is a toxic chemical compound with the chemical formula COCl₂. It consists of one carbon atom, one oxygen atom, and two chlorine atoms. Although its name might suggest a connection to phosphorus, there is no phosphorus in phosgene. Instead, the name originates from the Greek words phos meaning light and genes meaning born or produced, because phosgene was first synthesized by exposing a mixture of carbon monoxide and chlorine gas to sunlight.
The question mentions two specific clues to identify the non-carbon elements:
- A group 16 element in the second row of the periodic table.
- A group 17 element in the third row of the periodic table.
The periodic table is organized into groups (vertical columns) and periods or rows (horizontal rows).
- Group 16 elements are also known as the chalcogens. In the second row of the periodic table, the group 16 element is oxygen (O), which has the atomic number 8. Oxygen is a non-metal and is essential in many compounds including water and carbon dioxide.
- Group 17 elements are known as the halogens. In the third row of the periodic table, the group 17 element is chlorine (Cl), with the atomic number 17. Chlorine is a highly reactive element that commonly forms compounds with other elements, such as in sodium chloride (NaCl) and phosgene.
Phosgene’s structure is simple: a central carbon atom double-bonded to an oxygen atom and single-bonded to two chlorine atoms. It was used as a choking agent during World War I due to its deadly effects on the respiratory system.