Concept:The modern periodic table orders elements by the number of protons in the nucleus, which is the atomic number.
Explanation:In the modern periodic table, elements are arranged from left to right in order of increasing atomic number, denoted as
Z.
The atomic number
Z equals the number of protons in the nucleus of an atom.
The number of protons is also called the nuclear charge because each proton contributes a charge of
+1.
Therefore, increasing atomic number means increasing positive charge on the nucleus.
Arranging by atomic mass was used in early versions of the table, but it caused some elements to be placed in the wrong groups.
Relative isotopic mass refers to the mass of a specific isotope compared with carbon-12, not the basis for the periodic table order.
Thus, the correct basis for listing the elements is the nuclear charge.
Answer:D. nuclear charge