Q.59. Given below are two statements : Statement (I): The first ionisation enthalpy of the elements

Q: What is the correct answer for this exam Chemistry Q59?

The correct answer is D. **Statement (I):** The first ionization enthalpy generally increases across a period due to increasing nuclear charge and decreasing atomic size. However, there are exceptions. The general trend for the elements Na, Mg, Al, Si, P, S, Cl, Ar is: Na Al S < Cl < Ar. Specifically, for Na, Mg, Cl, Ar: * Na (Group 1): Lowest ionization enthalpy. * Mg (Group 2): Higher than Na due t

Q: Q.59. Given below are two statements : Statement (I): The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order Na > Mg > Cl > Ar Statement (II): Among Ca, Al, Fe and B, the…

The correct answer is D. **Statement (I):** The first ionization enthalpy generally increases across a period due to increasing nuclear charge and decreasing atomic size. However, there are exceptions. The general trend for the elements Na, Mg, Al, Si, P, S, Cl, Ar is: Na Al S < Cl < Ar. Specifically, for Na, Mg, Cl, Ar: * Na (Group 1): Lowest ionization enthalpy. * Mg (Group 2): Higher than Na due t

Q: What are the options for this this exam Chemistry question?

A. Both Statement I and Statement II are true · B. Both Statement I and Statement II are false · C. Statement I is true but Statement II is false · D. Statement I is false but Statement II is true

Question

Q.59. Given below are two statements : Statement (I): The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order Na > Mg > Cl > Ar Statement (II): Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca. In the light of the above statements, choose the correct answer from the options given below :

FirstInTest · Accepted Answer

**Statement (I):** The first ionization enthalpy generally increases across a period due to increasing nuclear charge and decreasing atomic size. However, there are exceptions. The general trend for the elements Na, Mg, Al, Si, P, S, Cl, Ar is: Na < Mg > Al < Si < P > S < Cl < Ar. Specifically, for Na, Mg, Cl, Ar: * Na (Group 1): Lowest ionization enthalpy. * Mg (Group 2): Higher than Na due to stable s$^2$ configuration. * Cl (Group 17): High ionization enthalpy due to high effective nuclear charge. * Ar (Group 18): Highest ionization enthalpy in the period due to stable noble gas configuration. So, the order should be Na < Mg < Cl < Ar. Statement (I) says Na > Mg > Cl > Ar, which is incorrect. **Statement (II):** We need to compare the third ionization enthalpy (IE$_3$) for Ca, Al, Fe, and B. * **Ca (Calcium):** Electronic configuration is $[Ar] 4s^2$. IE$_1$ removes one $4s$ electron, IE$_2$ removes the second $4s$ electron. After removing two electrons, Ca becomes Ca$^{2+}$ with a stable noble gas configuration ($[Ar]$). Removing a third electron from this stable configuration requires a very high amount of energy. So, IE$_3$ for Ca is very high. * **Al (Aluminum):** Electronic configuration is $[Ne] 3s^2 3p^1$. IE$_1$ removes $3p^1$, IE$_2$ removes $3s^1$, IE$_3$ removes the last $3s^1$ electron. After removing three electrons, Al becomes Al$^{3+}$ with a stable noble gas configuration ($[Ne]$). IE$_3$ is not exceptionally high compared to IE$_4$. * **Fe (Iron):** Electronic configuration is $[Ar] 3d^6 4s^2$. IE$_1$ removes $4s^1$, IE$_2$ removes $4s^1$, IE$_3$ removes $3d^1$. Fe$^{3+}$ has a stable half-filled $3d^5$ configuration. IE$_3$ is not exceptionally high. * **B (Boron):** Electronic configuration is $[He] 2s^2 2p^1$. IE$_1$ removes $2p^1$, IE$_2$ removes $2s^1$, IE$_3$ removes the last $2s^1$ electron. After removing three electrons, B becomes B$^{3+}$ with a stable noble gas configuration ($[He]$). IE$_3$ is not exceptionally high compared to IE$_4$. Among these, Ca has an exceptionally high third ionization enthalpy because it involves removing an electron from a very stable noble gas core configuration (Ca$^{2+}$ has an Argon-like configuration). So, Statement (II) is true. Therefore, Statement (I) is false but Statement (II) is true.

Answer

Both Statement I and Statement II are true

Answer

Both Statement I and Statement II are false

Answer

Statement I is true but Statement II is false

Answer

Statement I is false but Statement II is true

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