11th Class Chemistry Classification of Elements and Periodicity in Properties

  • question_answer 77)   Ionisation enthalpies of elements of second period are given below : Ionisation enthalpy (kcal\[mo{{l}^{-1}}\]): 520, 899, 801, 1086, 1402, 1314, 1681, 2080 Match the correct enthalpy with the elements and complete the graph given in the following figure. Also symbols of elements with their atomic numbers.

    Answer:

      The second period elements with their symbols, atomic numbers and ionisation enthalpies are given below :  

    Symbol Li Be B C N O F Ne
    At. Number 3 4 5 6 7 8 9 10
    \[\Delta {{H}_{1}}(kJ\,mo{{l}^{-1}})\] 520 899 801 1086 1402 1314 1681 2080
      In a period, the value of ionisation enthalpy increases from left to right with breaks where the atoms have somewhat stable configurations. Be and N have higher values than expected. Be has fully filled orbital while N has half filled orbitals. Be: \[1{{s}^{2}},2{{s}^{2}}\] N : \[1{{s}^{2}},2{{s}^{2}},2p_{x}^{1},2p_{y}^{1}2p_{z}^{1}\] Complete the graph yourself and compare with the graph given in problem 38.


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