Answer:
The atomic number of the element in this notation is 15.
Step-by-step explanation:
The X notation for an atom provides information about its atomic number and mass number. The atomic number is the number of protons in the nucleus of an atom, which determines its chemical properties and identity as an element. The mass number is the sum of the number of protons and neutrons in the nucleus.
In the notation "32 on 15 X", the number on the top (32) represents the mass number of the atom, which is the total number of protons and neutrons in the nucleus. The number on the bottom (15) represents the atomic number of the atom, which is the number of protons in the nucleus.
Therefore, the atomic number of the element in this notation is 15.