why can the electron gain enthalpy be endothermic or exothermic?
and why not endothermic alone
how can it be exothermic?
why can the electron gain enthalpy be endothermic or exothermic?
and why not endothermic alone
how can it be exothermic?
Electron Gain Enthalpy or Electron Affinity is the amount of energy released when an isolated, neutral, gaseous atom takes up an extra electron to form uninegative gaseous ions.
X(g) + e− ----→ X− .
A reaction with negative energy of reaction is termed as exothermic and those with positive energy of reaction is termed as endothermic.
As a general rule, electron gain enthalpy becomes more negative with increase in atomic number across a period and less negative as we go down a group. Now this energy will be negative for those elements which have a tendency to gain electrons. The negative value of electron gain enthalpy denotes that energy is given out and a positive value denotes that energy is absorbed when an electron is gained by an atom. More is the electronegativity of an atom, more is its tendency to accept electrons and more is the energy released when it accepts electrons. Therefore for elements with high electronegativity, the electron gain enthalpy is negative. As an electropositive element has more tendency to lose electrons than to gain electrons, therefore for these elements (like Na, K, Ca etc) the electron gain enthalpy will either be positive or will have small negative values.
Electron Gain Enthalpy or Electron Affinity is the amount of energy released when an isolated, neutral, gaseous atom takes up an extra electron to form uninegative gaseous ions.
X(g) + e− ----→ X− .
A reaction with negative energy of reaction is termed as exothermic and those with positive energy of reaction is termed as endothermic.
As a general rule, electron gain enthalpy becomes more negative with increase in atomic number across a period and less negative as we go down a group. Now this energy will be negative for those elements which have a tendency to gain electrons. The negative value of electron gain enthalpy denotes that energy is given out and a positive value denotes that energy is absorbed when an electron is gained by an atom. More is the electronegativity of an atom, more is its tendency to accept electrons and more is the energy released when it accepts electrons. Therefore for elements with high electronegativity, the electron gain enthalpy is negative. As an electropositive element has more tendency to lose electrons than to gain electrons, therefore for these elements (like Na, K, Ca etc) the electron gain enthalpy will either be positive or will have small negative values.
