Explain trend of electron gain enthalpy in the periods & group

1.	Explain trend of electron gain enthalpy in the periods & group
Answer» The electron gain enthalpy of halogens is highly negative because it needs only one electron to achieve nearest noble gas configuration. And for noble gases, it is highly positive because the extra electron has to be placed in the next higher principal quantum level which requires lots of energy.<br>Electron gain enthalpy (ΔegH) is defined as the enthalpy change associated with an isolated gaseous atom (X) when it gains an electron to form its corresponding anion. The reaction can be given as below:X(g)+e−→X−(g)On the basis of nature of the element, the process of accepting electron in an atom can either be exothermic or endothermic. In general, energy is released when an electron is added to an atom and the electron gain enthalpy for such elements is negative.

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