Question

The number of d-electrons in Fe2+ (Z = 26) is not equal to that of

A. p-electrons in Ne(Z = 10)
B. s-electrons in Mg(Z = 12)
C. d-electrons in Fe(Z = 26)
A. p-electrons in CI(Z = 17)​

Answer 1

Answer:

Size of isoelectronic species -

Smaller the value of z/e, larger the size of that species.Smaller z means effective nuclear charge is small hence size is large.

-

Fe(26) = 1s2 2s2 2p6 3s2 3p6 4s2 3d6

Fe2+ (26) = 1s2 2s2 2p6 3s2 3p6 4s1 3d5

Number of d electron in Fe2+ = -5

For Cl (17) = 1s2 2s2 2p6 3s2 3p5

so number of d electron in Fe2+ is same as number of P electron in cl

Option 1)

d - electrons in Fe (Z = 26)

Option is incorrect

Option 2)

p - electrons in Ne (Z = 10)

Option is incorrect

Option 3)

s - electrons in Mg (Z = 12)

Option is incorrect

Option 4)

p - electrons in CI (Z =17)

Option is correct