sentence: Black arsenic is similar to red phosphorus.
sentences_before: It is a semiconductor. Yellow arsenic is unstable and rare. It is the most toxic allotrope. It is a soft and waxy nonmetal, similar to white phosphorus. It turns into gray arsenic in light.
sentences_after: It is a brittle, black, and shiny nonmetal. It does not conduct electricity. Since gray arsenic is the most common, it is usually referred to as arsenic.
concept_name: black arsenic
headings: Arsenic Properties Physical properties
categories: Semimetals Chemical elements