Question

Which of the following has zero electron affinity
A.Radon
B.Nitrogen
C.Oxygen
D.Radium

Answer 1

Hint:To answer this question, you should recall the trends in the periodic table. The modern periodic law developed by Moseley states that the physical and chemical properties of elements are the periodic function of their atomic number. The atoms with a stable electronic configuration will have zero electron affinity.

Complete step by step answer:
Electron affinity is defined as the amount of energy released when an electron is added to an isolated neutral gaseous atom to form an anion. The factors that affect the electron affinity are Atomic size and nuclear charge. In case that the atomic size is small, then there will be greater electron gain enthalpy because the effective nuclear forces will be greater and the added electron will be held with more strength. Also, greater the nuclear charge more will be the value for electron gain enthalpy because an increase in nuclear charge will increase the effective nuclear force i.e. the strength of force the on-valence electrons.
The noble gases, alkali metals and alkali earth metals have electron affinity close to zero because these groups of elements do not particularly like to become anions as a tremendous amount of energy will be required in this process making the anion have a lot of energy and instability.
Therefore, Radon has electron affinity close to zero.

Hence, we can conclude that the correct answer to this question is option A.

Note:
Let us summarize the trends of fundamental properties of an element:
1.Atomic Radii and Ionic radii: The atomic radii and ionic radii of elements decrease while moving from left to right in a period.
2.Ionization Enthalpy: Across a period in the periodic table, ionization energy generally increases. For the trend in a group, ionization enthalpy decreases from top to bottom.
3.Electron gain enthalpy: Electron gain enthalpy becomes more negative as we move from left to right in a period. Electron gain enthalpy is negative when energy is released while accepting an electron. While it is positive when energy is supplied to an atom while adding an electron.