nativecros.blogg.se - Two main factors affecting atomic size trend

When the atomic size or atomic radius is large, the E.A will be smaller. The relationship between E.A and atomic size is given below: There are the following factors that affect electron affinity: Atomic size Exceptions to the trends of Electron Affinity.Here, the value of electron affinity decreases, and the addition of electrons becomes more and more difficult. Hence, it is an endothermic process.įor example, E.A for O -1 is -142 KJ., and for O 2- is +844 KJ. The negative ion repels the incoming electron. However, when a second electron is added to a uni-negative ion. So the first electron affinity values are always negative.

Where E 1 and E 2 stand for first and second electron affinity.Īdding the first electron to a neutral atom is an exothermic process.

However, it can be determined by the Born-Haber cycle. The value of electron affinity cannot be determined directly. It is also known as the electron gain enthalpy which is the amount of energy released when one mole of a gaseous neutral atom is converted to its anions by the addition of electrons.Į.A is expressed in electron volts, kJ/mole, and Kcal/mole. However 2 nd E.A is always positive due to the repulsion between the anion and the incoming electron. It has a negative value for most of the atoms which means that energy is released upon the addition of an electron to an atom. Specifically, it is the tendency of an atom to attract electrons.

Electron affinity (E.A) is the amount of energy released when an electron is added to a neutral gaseous atom or molecule to form a negative ion.