Modern Periodic Table — Chemistry STD 11 Science — Question
Maharashtra BoardEnglish MediumSTD 11 ScienceChemistryModern Periodic Table2 Marks
Question
Give reason: First period in the modern periodic table contains only two elements.
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Answer
Elements present in the first period i.e., H and He contain only one shell which is also their valence shell and can accommodate maximum two electrons.
As first shell can accommodate only two electrons, first period ends at He which has a complete duplet. Hence, first period in the modem periodic table contains only two elements.
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