Ncert Exercises & Solutions

Match the correct ionization enthalpies and electron gain enthalpies of the following elements.

Codes

Hint: Most electronegative element has most negative electron gain enthalpy

(i) Most reactive non-metal has high

∆_{} H_{1}

and

∆_{} H_{2}

and most negative

∆_{eg} H

. Therefore, the element is B.

(ii) Most reactive metal has low

∆_{} H_{1}

and high

∆_{} H_{2}

(because the second electron has to be lost from noble gas configuration) and has small negative

∆_{eg} H

. Therefore, the element is A.

(iii) Noble gases are the least reactive elements. They have very high

∆_{} H_{1}

and

∆_{} H_{2}

and have positive

∆_{eg} H

values. Thus, the element is D.

(iv) Metal forming binary halides are alkaline earth metals. They have

∆_{} H_{1}

and

∆_{} H_{2}

values little higher than those of most reactive metals (such as A) and have comparatively slightly less negatice

∆_{eg} H

values. Thus, the element is C.