(i) \(O\) and \(F\) are present in the same period of the periodic table. An \(F\) atom has one proton and one electron more than \(O\) and as an electron is being added to the same shell, the atomic size of \(F\) is smaller than that of \(O\). As \(F\) contains one proton more than \(O\), its nucleus can attract the incoming electron more strongly in comparison to the nucleus of \(O\) atom. Also, \(F\) needs only one more electron to attain the stable noble gas configuration.
Hence, the electron gain enthalpy of \(F\) is more negative than that of \(O\).
(ii) \(F\) and \(Cl\) belong to the same group of the periodic table. The electron gain enthalpy usually becomes less negative on moving down a group. However, in this case, the value of the electron gain enthalpy of \(Cl\) is more negative than that of \(F\). This is because the atomic size of \(F\) is smaller than that of \(Cl\). In \(F\), the electron will be added to quantum level \(n\) = \(2\), but in \(Cl\), the electron is added to quantum level \(n\) = \(3\). Therefore, there are less electron repulsions in \(Cl\) and an additional electron can be accommodated easily.
Hence, the electron gain enthalpy of \(Cl\) is more negative than that of \(F\).
Was this answer helpful?
0
0
Top Questions on Electronic Configurations Of Elements And The Periodic Table
Classification of Elements & Periodicity in Properties
Since many elements were being discovered in the 19th century and the study of these elements individually was proving difficult, classification of elements was made necessary.
Classification by Johann Dobereiner - German chemist Johann Dobereiner classified certain elements on the basis of their similar properties in the groups of continuing - three elements each. These groups were called ‘triads’. In every triad, the atomic weight of the middle element was equal to the average of the atomic weights of the first and third elements.
Newlands Law of Octaves - The elements were arranged in increasing order of their atomic weights and found that every 8th element shows similarity with the 1st element.
Mendeleev’s Periodic Table - The arrangement of all 63 elements in rows or columns in order of their atomic weight was made by Mendeleev. He left some space for corresponding elements in his periodic table which were not even discovered till then. Although he predicted the properties of those elements through his periodic classification of elements.
Modern Periodic Law - The properties of the elements of the modern periodic law are periodic functions of their atomic numbers.
