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.


      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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