The composition of the nuclei of three atomic species X, Y, and Z are given as follows. [X: 18 protons, 19 neutrons; Y: 17 protons, 18 neutrons; Z: 17 protons, 20 neutrons] Explain the relation between the following:
Y and Z
Y and Z have the same number of protons (17), giving them the same atomic number. However, they have different numbers of neutrons (18 and 20), resulting in different mass numbers (35 and 37). Atoms with the same atomic number but different mass numbers are called isotopes. Hence, Y and Z are isotopes.
Z and X
Z has 17 protons and 20 neutrons, while X has 18 protons and 19 neutrons. This means Z and X have different atomic numbers (17 and 18) but the same mass number (37). Therefore, the relation between Z and X is that they are atoms of different elements sharing the same mass number.
Explanation
The question tests the understanding of atomic composition and related terminology. For Y and Z, since the number of protons is identical (17) but the number of neutrons differs, they fit the textbook's definition of isotopes. For Z and X, the atomic numbers differ but the mass numbers are equal; while the term 'isobars' is standard for this relation, it is not explicitly defined in the provided context, so the relation is described by comparing their atomic and mass numbers.