Question

in a noble gas, total number of p electrons is equal
to sum of d and s electrons. The minimum
atomic
number possible for that element is X while its
period number in modern periodic table is Y. The
value of X + Y is

Answer 1

It has given that,

in a noble gas, total number of p electrons is equal to sum of d and s electrons. The minimum number possible for that element is X while its period number in Morden periodic table is Y.

To find : The value of (X + Y).

solution : we know, He , Ne and Ar doesn't have d subshell. now next noble gas is Kr ( Krypton) it has d subshell. let's try to check it.

electronic configuration of Kr = 1s², 2s², 2p⁶, 3s², 3p⁶ , 4s² , 3d¹⁰, 4s² , 4p⁶

here no of electrons in S - subshells = 2 + 2 + 2 + 2 = 8

no of electrons in P - subshells = 6 + 6 + 6 = 18

no of electrons in d - subshells = 10

here, no of electrons in p - subshells = no of electrons in s - subshells + no of electrons in d - subshells

so, element is nother other than Krypton.

atomic no of Krypton, X = 36

and period number, Y = 4

so, X + Y = 36 + 4 = 40

Therefore the value of X + Y = 40