Explain in detail About The position of "Hydrogen" and "Helium" in Modern Periodic Table ?

 

Dear student,

Please find below the solution of your asked query.

In the periodic table the position of hydrogen is ambiguous but generally it is placed at the top of group 1 above the alkali metals. This is because the electronic configuration of hydrogen is similar to alkali metals. Both have 1 valence electron each. However because of its small size the properties of hydrogen do not match with the alkali metals. Sometimes hydrogen is not included in any group of the periodic table and it is treated as a special element.
In modern periodic table helium is placed in 18 group although unlike other noble gases it has 2 electrons in its valence shell but its duet is complete and it behave as chemically inert.Also like noble gases it is monoatomic in nature.

Hope this solution clears the concept regarding the topic.

Thanks

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