Which of the following elements is different in physical appearance from the others?

Among the elements listed—arsenic (As), phosphorus (P), antimony (Sb), and bismuth (Bi)—phosphorus stands out due to its distinct non-metallic and colorful forms. Phosphorus exists in several allotropic forms, including white, red, and violet phosphorus, each having a different color and appearance. For example, white phosphorus is waxy and translucent, red phosphorus is reddish-brown powder, and violet phosphorus has a dark, crystalline form.

In contrast:

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  Arsenic (As) is a metalloid with a metallic gray appearance and crystalline structure.

  
  


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  Antimony (Sb) is also a metalloid with a silvery metallic luster, brittle in solid form.

  
  


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  Bismuth (Bi) is a post-transition metal with a shiny silver-pink metallic luster and crystalline habit.

  
  

These three elements have metallic or semi-metallic characteristics, giving them a similar grayish metallic appearance, which contrasts sharply with phosphorus. This difference in appearance is due to phosphorus being a non-metal, which lacks the free electrons responsible for metallic luster seen in metalloids and metals.

This MCQ highlights an important concept in inorganic chemistry: the classification of elements based on physical and chemical properties. While arsenic, antimony, and bismuth are part of Group 15 and share metallic characteristics, phosphorus is a non-metal and therefore differs significantly in both physical appearance and chemical behavior.

Hence, the correct answer is Phosphorus (B), making it visually distinct from the other listed elements.