Question

19. A 62 kJ (unfavorable) change in electron affinity (EA) is observed in going from silicon (EAsi-134 kJ/mmol) to phosphorous (EAp-72 kJ/mol). What accounts for the unexpected change in the EA of phosphorous? Elechon hy (a) It's due to increasing effective nuclear charge It's not unexpected; it follows the periodic trend, 1 (c) It's due to electron-electron repulsion (d) It's opposite the expected trend (e) It's due to having to add an electron to an unfilled subshell e toe nd a

Written explanations as to why the choices are correct or incorrect

Answer 1

The right answer is C here because,

If we compare the electronic configuration of Silicone and Phosphorus we know that,

Si contains 2 electrons in 3p orbital and in Phosphorus it contains 3 electrons means its have a half filed orbital and one elctron more than silicone so if we added a electron to Phosphorus then it will gets repelled by 3 electrons of 3p orbital and hence less energy will be released so the value of Phosphorus is less than silicone