What types of elements are classified as heavy metals and may be harmful to human health?

Heavy metals are typically defined as metallic elements that have a high atomic weight and a density greater than 5 g/cm³. These elements can be toxic to humans and other living organisms even at low concentrations. Among the options provided, arsenic, lead, and mercury are all well-known heavy metals associated with significant health risks.

Arsenic is a toxic element that can cause various health problems, including skin lesions, developmental effects, and increased risk of cancer. Lead exposure can impair cognitive functions and neurological development, particularly in children. Mercury is another notorious heavy metal, linked to neurological and behavioral disorders, as well as serious health issues related to its accumulation in biological systems.

In contrast, the other choices consist of elements that are classified as essential nutrients or metals with lower toxicity levels. Aluminum and copper, iron and zinc, as well as calcium and magnesium are not typically categorized as heavy metals, as they either play crucial roles in biological functions when in trace amounts or do not exhibit significant toxic effects relevant to human health at typical exposure levels. As such, arsenic, lead, and mercury stand out as harmful heavy metals, making this choice the most accurate regarding the inquiry about elements harmful to human health.