The second line of Lyman series of H-atom coincides with the sixt line of Paschen series of an ionic species 'X'. Identify 'X'. (Suppose the value of Rydberg constant, R is same in both cases)

Explanation

For the second line of Lyman series of H-atom,
`overline(v)=R((1)/(1^(2))-(1)/(3^(2)))` . . .[1]
For the sixth line of Paschen series of the species 'X' with atomic number Z, `overline(v)=RZ^(2)((1)/(3^(2))-(1)/(9^(2)))` . . . [2]
Since second line of Lyman series coincides with the sixth line of Paschen series of the species 'X'. hence we can equate (1) and (2), ie., `R((1)/(1^(2))-(1)/(3^(2)))=RZ^(2)((1)/(3^(2))-(1)/(9^(2)))`
or, `8/9 =Z^(2)xx(8)/(81)" or, "Z^(2)=9` ltbr. or, Z=3 `therefore`The ionic species would be `Li^(2+)`.