Number of CORRECT information among given : (1) In general group-6 elements have greater melting point than group-12 elements in long form of modern periodic table. (2) For chromium 2 nd ionization en

Question

Number of CORRECT information among given :

(1) In general group-6 elements have greater melting point than group-12 elements in long form of modern periodic table.

(2) For chromium $2^{nd}$ ionization energy is greater but $3^{rd}$ ionization is lesser as compared to iron. (3) In 3d-series Cu has highest density but Sc has lowest density. (4) Zn has minimum enthalpy of atomisation among 3d-series. (5) Gold has greater density as compared to copper. (6) Ionic radius of $Ni^{+ 2}$ is least among all existing $M^{+ 2}$ metal ion of 3d-series. (7) For $M^{+ 2} / M$ value of standard electrode potential $E^{⊖} / V$ is maximum for $Cu^{+ 2} / Cu$

TestHub · Accepted Answer

Statement (2) is incorrect: The third ionization energy ( $I E_{3}$ ) of chromium ( $3 d^{4} \to 3 d^{3}$ ) is greater than that of iron ( $3 d^{6} \to 3 d^{5}$ ) because removing an electron from iron leads to a highly stable, half-filled $3 d^{5}$ configuration.

Statements (1), (3), (4), (5), (6), and (7) are all correct: Group-6 has stronger metallic bonds than Group-12; density increases across the 3d-series (Sc lowest, Cu highest) and down the group (Au > Cu); Zn has the lowest enthalpy of atomization due to zero unpaired d-electrons; Ni²⁺ has the smallest ionic radius in the 3d series; and Cu²⁺/Cu is the only positive (maximum) standard reduction potential in the series.

Therefore, the number of correct statements is 6.

Chemistry - Complete d-block Question with Solution | TestHub

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