Out of the elements phosphorus (P), sulphur (S), chlorine (Cl) and fluorine (F), the elements having the most negative and least negative electron gain enthalpy, respectively are<\/p>\n
[amp_mcq option1=”Cl and P” option2=”F and S” option3=”F and Cl” option4=”P and S” correct=”option1″]<\/p>\n
Let’s consider the given elements:
\n– F (Period 2, Group 17)
\n– Cl (Period 3, Group 17)
\n– S (Period 3, Group 16)
\n– P (Period 3, Group 15)<\/p>\n
Comparing F and Cl (Group 17): Although the general trend is less negative down a group, Cl has a more negative electron gain enthalpy (-349 kJ\/mol) than F (-328 kJ\/mol). This is an anomaly due to the very small size of F, where the added electron experiences significant repulsion from existing electrons in the compact 2p subshell.
\nComparing Cl and S (same period, different groups): Electron gain enthalpy becomes more negative across the period. Cl is in Group 17, S is in Group 16. So, Cl should have a more negative value than S. (Cl: -349 kJ\/mol, S: -200 kJ\/mol). This is consistent.
\nComparing S and P (same period, different groups): S is in Group 16, P is in Group 15. Group 15 elements have unusually low (less negative) electron gain enthalpies due to the stable half-filled configuration. So, P should have a less negative value than S. (S: -200 kJ\/mol, P: -74 kJ\/mol). This is consistent.<\/p>\n
Ranking the elements by electron gain enthalpy from most negative to least negative:
\nCl (-349) > F (-328) > S (-200) > P (-74)<\/p>\n
The element with the most negative electron gain enthalpy is Cl.
\nThe element with the least negative electron gain enthalpy is P.<\/p>\n