Explain the following: (i) Why argon (atomic mass `= 39.94)` has been placed before potassium (atomic mass `= 39.10)` in the Modern periodic table? (i

Monjur Alahi

Explain the following:
(i) Why argon (atomic mass `= 39.94)` has been placed before potassium (atomic mass `= 39.10)` in the Modern periodic table?
(ii) There are only `14` anthanides and only `14` actinides in Modern peridoic table.


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Salim Ahmed Kawsar

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Correct Answer - (i) In modern periodic table, elements have been placed in order of their increasing atomic numbers. The atomic number of argon is 18 and that of potassium is 19. Thus, argon has been placed before potassium
(ii) In lanthanides and actinides, the differentiating electron enters to `(n -2)` f-subshell. The maximum capacity of f-subshell is of 14 electrons. Thus, there are only 14 anthanides `(4f^(1-14))` and only 14 actinides `(5f^(1-14))`.
(i) In modern periodic table, elements have been placed in order of their increasing atomic numbers. The atomic number of argon is 18 and that of potassium is 19. Thus, argon has been placed before potassium
(ii) In lanthanides and actinides, the differentiating electron enters to `(n -2)` f-subshell. The maximum capacity of f-subshell is of 14 electrons. Thus, there are only 14 anthanides `(4f^(1-14))` and only 14 actinides `(5f^(1-14))`.

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