Question

Which one of the following is the correct order of given isotopes?

I. \( T_2 > D_2 > P_2 \quad \text{(order of boiling point)} \)

II. \( T_2 > D_2 > P_2 \quad \text{(order of bond energy)} \)

III. \( T_2 = D_2 = P_2 \quad \text{(order of bond length)} \)

IV. \( T_2 < D_2 < P_2 \quad \text{(order of reactivity with } Cl_2 \text{)} \)

• A. I and II
• B. III and IV
• C. II, III and IV
• D. All of these

Hint:

When comparing isotopes of hydrogen, remember that heavier isotopes have higher boiling points and bond energies, while lighter isotopes have shorter bond lengths and higher reactivity with halogens like chlorine.

Answer 1

The Correct Option is D

We are asked to analyze the order of isotopes \( {T}_2 \), \( {D}_2 \), and \( {P}_2 \) with respect to four properties: boiling point, bond energy, bond length, and reactivity with chlorine. 
I. Order of boiling point: The boiling point of hydrogen isotopes increases with increasing mass. Therefore, the order of boiling points is: \[ {T}_2>{D}_2>{P}_2 \] This is because \( {T}_2 \) (tritium) has the heaviest atoms, followed by \( {D}_2 \) (deuterium), and \( {P}_2 \) (protium) has the lightest atoms. 
II. Order of bond energy: The bond energy increases as the mass of the hydrogen isotope decreases. Since the bond energy is inversely related to the mass of the isotopes, the order of bond energy is: \[ {T}_2>{D}_2>{P}_2 \] This follows because \( {P}_2 \) (protium) has the weakest bond due to its lighter mass, and \( {T}_2 \) (tritium) has the strongest bond. 
III. Order of bond length: The bond length remains the same for all three isotopes because the bond length is determined by the type of atom, not the mass. Therefore, the order of bond lengths is: \[ {T}_2 = {D}_2 = {P}_2 \] 
IV. Order of reactivity with \( {Cl}_2 \): Reactivity with chlorine decreases as the mass of the hydrogen isotope increases. Therefore, the order of reactivity is: \[ {T}_2<{D}_2<{P}_2 \] This is because the lighter the isotope, the more reactive it is with chlorine. 
Conclusion: All of the given orders are correct. Therefore, the correct answer is \( \boxed{{D}} \).