Periodic law Transitional Reasoning Download PDF

Questions

1. 1.

   When constructing early versions of the periodic table based on increasing atomic mass, scientists encountered contradictions such as placing tellurium (127.60 u) before iodine (126.90 u). Despite having a greater atomic mass, tellurium had to precede iodine so that iodine could be grouped with chemically similar halogens like chlorine and bromine. Which statement best explains why organizing elements by atomic number resolves this contradiction and forms the foundation of the modern periodic law?

   • A) Chemical and physical properties recur periodically when elements are arranged by increasing nuclear charge because atomic number determines valence electron configuration.
   • B) Total isotopic mass directly governs valence patterns, ensuring that heavier elements always exhibit nonmetallic chemical behavior.
   • C) The number of neutrons in the atomic nucleus dictates group reactivity, aligning elements with similar neutron counts into vertical columns.
   • D) Elements located in the same horizontal period share identical numbers of valence electrons, which overrides discrepancies in atomic mass.