Phosphorus (p) is the element with the atomic number 15. which of the
following correctly compares 31p and 32p, which are two isotopes of
phosphorus?

Explanation:

   Isotopes:

                          ₁₅³¹P   and     ₁₅³²P

     Given parameters:

       ₁₅³¹P                                                   ₁₅³²P          

   Mass number = 31                                    32

   Atomic number = 15                                 15

The two atoms are isotopes. Now let us derive numbers of their subatomic particles

                       ₁₅³¹P                                             ₁₅³²P  

Protons              15                                                 15

Electrons           15                                                  15

Neutrons         (31-15) = 16                               (32-15) = 17

Because they are isotopes, they differ in the number of neutrons alone.

Isotopy is the existence of two or more atoms of the same element having the same atomic number but different mass numbers due to the differences  in the number of their neutrons.

We clearly see that the mass number and number of neutrons pertaining to the atom differs. This makes them isotopes.

Learn more:

Isotope

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