(∆E), The energy required to excite an electron in an atom of hydrogen from n=1 to n=2 is ∆E (difference in energy E2 and E1 ) Values of E2 and E1 are, E2=
−1.312×106×(1)2
(2)2
=−3.28×105Jmol−1 ∆E is given by the relation, E1=−1.312×106Jmol−1 ∴∆E=E2−E1=[−3.28×105]−[−1.312×106]Jmol−1 =(−3.28×105+1.312×106)Jmol−1 =9.84×105Jmol−1