The elements in the periodic table are listed in order of increasing

Analysis

The question asks for the fundamental property that determines the arrangement of elements in the modern Periodic Table.

Concept Explanation

In the early days of chemistry, scientists like Dmitri Mendeleev arranged elements based on their atomic mass. However, this led to several inconsistencies (such as the placement of Tellurium and Iodine).

In 1913, Henry Moseley discovered that the properties of elements are a periodic function of their atomic number (the number of protons in the nucleus). Since the number of protons is equal to the number of electrons in a neutral atom, and the number of protons defines the nuclear charge, the modern Periodic Table is arranged by increasing atomic number, which corresponds directly to the increasing positive charge of the nucleus.

Step-by-Step Solution

1. Evaluate Option A: "Relative atomic number" is not a standard term; we simply use "atomic number."
2. Evaluate Option B: Atomic mass was the old method, which was replaced because it does not account for isotopes correctly.
3. Evaluate Option C: Relative isotopic mass refers to specific isotopes, not the elements themselves as they appear in the table.
4. Evaluate Option D: The atomic number of an element is defined by the number of protons in its nucleus. Since each proton carries a positive charge, the atomic number is effectively the nuclear charge. As you move from one element to the next in the periodic table, you are adding one proton, thereby increasing the nuclear charge by one unit.

Exam Tip

Always remember: Mendeleev = Atomic Mass, but Modern Periodic Law = Atomic Number (Nuclear Charge). If you see "Atomic Number" and "Nuclear Charge" as options, they are essentially the same thing, but "Nuclear Charge" is the more fundamental physical description.