How can two atoms of the same chemical element be different?

A.
They may be different isotopes of the element. Each isotope of the same element has a different number of neutrons.

B.
They may be different allotropes of the element. Each allotrope of the same element has a different number of electrons.

C.
They may be different isotopes of the element. Each isotope of the same element has a different number of electrons.

D.
They may be different allotropes of the element.

Question

How can two atoms of the same chemical element be different?  
 
 

 
 

  

  A. 
  They may be different isotopes of the element. Each isotope of the same element has a different number of neutrons.   
   

 
 

  

  B. 
  They may be different allotropes of the element. Each allotrope of the same element has a different number of electrons.   
   

 
 

  

  C. 
  They may be different isotopes of the element. Each isotope of the same element has a different number of electrons.   
   

 
 

  

  D. 
  They may be different allotropes of the element.

abb0t · Answer

due to isotopes, different number of neutrons.