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Solution


Q.

Which of the following statements are true                                      [2025]

A. Unlike Ga that has a very high melting point, Cs has a very low melting point.

B. On Pauling scale, the electronegativity values of N and Cl are not the same.

C. Ar,K+,Cl-,Ca2+ and S2- are all isoelectronic species.

D. The correct order of the first ionization enthalpies of Na, Mg, Al and Si is Si > Al > Mg > Na.

E. The atomic radius of Cs is greater than that of Li and Rb.

Choose the correct answer from the options given below:
1 C and D only  
2 A, C and E only  
3 A, B and E only  
4 C and E only  

Ans.

(4)

A. Ga has melting point of 303 K whereas Cs has melting point of 302 K.

B. On Pauling scale, the electronegativity values of N and Cl are same i.e., 3.0.

C. All the given species are isoelectronic as all have same number of electrons (i.e., 18).

D.The correct order of first ionisation enthalpies is
                                         Si>Mg>Al>Na 
  I.E.1 (in kJ mol-1):786  737  577  496 

E. As atomic radius increases on going down the group, hence the given statement is correct.