Chemistry S & P Block Elements MDCAT 2019
PMDC Verified Question 77 of 104
Modern periodic table is arranged in ascending order of?
A
Atomic mass
B
Mass number
C
Nucleon number
D
Proton number
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Proton number
Concept:

The periodic law underwent a major revision after Henry Moseley's X-ray experiments, which revealed that atomic number is the fundamental property of an element.

Solution:

  • Dmitri Mendeleev originally arranged the periodic table by increasing atomic mass, which led to several inconsistencies (like Tellurium and Iodine).
  • Moseley discovered the atomic number, which is exactly equal to the number of protons in the nucleus.
  • The Modern Periodic Law states that the physical and chemical properties of elements are periodic functions of their proton number (atomic number).


Why other options are incorrect:

  • Options A, B, & C: Atomic mass, mass number, and nucleon number all relate to the sum of protons and neutrons. Arranging by mass leads to isotopic confusion and elemental misplacement.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

Previous Question All S & P Block Elements MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App