The correct option is A,
Isotopes are atoms of an element, which have the same number of protons but different number of neutrons in the nucleus of the atom. Thus, isotopes have the same atomic number but different mass number.
Looking at the options given above, you will discover that Chlorine which is given in option A is correct. Both type of chlorine has the same atomic number, which is 17, but they have different atomic masses, the atomic mass of the first one is 35 while that of the second one is 37.<span />
        
             
        
        
        
Hello!
The mass number in isotope notation is denoted A, the atomic number is denoted as Z, and the element is denoted as X. 
In the given isotope, the mass of the isotope is 212 amu, and the atomic number is 82. 
We know that the number of electrons, and protons are equal to the atomic number. Therefore, there are 82 protons. Also, to find the number of neutrons, we subtract the atomic number from the atomic mass. 
212 - 82 = 130 neutrons 
<u>Final answers</u>:  
- Atomic Number: 82 
- Mass number: 212 
- Number of Protons: 82
- Number of Neutrons: 130 
 
        
             
        
        
        
Answer:
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Explanation: