Which of the following is classified as heavy metal?

Lead is classified as a heavy metal due to its density and toxicity. Heavy metals are generally defined as metals with a high atomic weight and a density greater than 5 g/cm³. Lead not only meets these criteria but is also known for its harmful effects on human health and the environment. Exposure to lead can lead to serious health issues, making it a significant concern in food safety and public health.

In contrast, the other options do not fit the classification of heavy metals. Carbon, while fundamental to organic compounds, is not classified as a heavy metal. Sodium is an alkali metal, which is lighter and does not possess the same toxicity associated with heavy metals. Chlorine is a non-metal and primarily known for its use in disinfectants and industrial applications, rather than for any heavy metal characteristics. Understanding this classification helps highlight the importance of monitoring heavy metals like lead in food products to ensure safety and compliance with health regulations.