d and f-Block ElementsMedium
Question
The correct order of first $\left( \Delta_{i}H_{1} \right)$ and second $\left( \Delta_{i}H_{2} \right)$ ionisation enthalpy values of cr and Mn are :
A. $\Delta_{i}H_{1}:Cr > Mn$
B. $\Delta_{i}H_{2}:Cr > Mn$
C. $\Delta_{i}H_{1}:Mn > Cr$
D. $\Delta_{i}H_{2}:Mn > Cr$
Choose the correct answer from the options given below :
Options
A.A and B only
B.B and C only
C.A and D only
D.C and D only
Solution
Sol. [Key Concept: With $Cr = \lbrack Ar\rbrack 3d^{5}4s^{1}$ and $Mn = \lbrack Ar\rbrack 3d^{5}4s^{2}$: ${IE}_{1}$ is higher for Mn ($Mn > Cr$) while ${IE}_{2}$ is higher for Cr ($Cr > Mn$), so statements B and C are correct.]
$${\ Cr - \lbrack Ar\rbrack 3{\text{ }d}^{5}4{\text{ }s}^{1} }{Mn - \lbrack Ar\rbrack 3{\text{ }d}^{5}4{\text{ }s}^{2} }{{IE}_{1} - Mn > Cr }{{IE}_{2} - Mn < Cr }$$
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