According to the Bohr's model in the atoms the electrons are moving around the nucleus in different shells. These shells are K, L, M, N etc.Complete step by step answer:
The principle quantum numbers of the shells are, for K is 1, for L is 2, for M is 3, for N is 4 etc.
According to the principal quantum number the total electrons can be filled in a shell is 2n2.
Therefore, the total electrons in K shell is 2, in L shell is 8, in M shell is 18 and so on.
Therefore, the electron distribution of X, Y, Z with atomic number 19,21 and 25 respectively.
|X (At. No=19)||2||8||9|
|Y (At. No.=21)||2||8||11|
|Z (At. No= 25)||2||8||15|
From this electronic distribution the number of electrons of X, Y, Z elements in the M shell are 9, 11, 15 respectively.
The order of electrons in M shell is\[\;z > y > x.\]
S From this electronic distribution the number of electrons of X, Y, Z elements in the M shell are 9, 11, 15 respectively.
The order of electrons in M shell is \[\;z > y > x.\]So, the correct option is, C.Note:
Reactivity or tendency to form chemical bonds with other atoms is determined by the number of electrons in the outermost shell of a particular atom. The maximum number of electrons can be filled in the K, L, M shells are 2, 8, 18 respectively.