Question

Define electron gain enthalpy and Electronegativity and How it varies along the groups & periods ?

Answer 1

the  electron gain enthalpy  is the energy to put the electron or put the negative charge on the element 
and Electronegativity is the negative charge on the element

Electron gain enthalpy becomes more and more negative from left to right in a period.

Answer 2

The electron gain enthalpy is the energy to put the electron or put the negative charge on elements and electronegativity is the charge on elements