The longest horizontal period found within the modern periodic table is___________________?
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Answer: A. 6th
Explanation
The sixth period accommodates filling of 6s, 4f, 5d, and 6p atomic orbitals. This intricate orbital filling sequence expands the row capacity to thirty-two elements. Inclusion of the lanthanide series makes it the longest horizontal period in the table. Modern periodic table arranges elements by atomic number into periods and groups. Electron shell capacities determine the maximum number of elements in each horizontal period. Transition metals and inner transition series contribute to the varying length of periods.
Materials science explores lanthanide elements found in the sixth period for advanced electronics. Periodic trends help chemists predict atomic radii and ionization energies across rows. Inorganic chemistry coursework emphasizes the unique chemical properties of sixth period elements. Seventh period contains radioactive synthetic elements but remains incomplete in total count. Second and third periods are short rows containing only eight elements each. Fifth period contains eighteen elements, which is fewer than the sixth period capacity.
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