The variation in ionization enthalpy along a series of transition elements is less pronounced than in a period of non-transition elements. While the first ionization enthalpy generally increases, the increase in the second and third ionization enthalpies is significantly higher along a series of transition elements.
Why does the variation in ionization enthalpy along a series of transition elements differ from that in a period of non-transition elements?
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The variation in ionization enthalpy along a series of transition elements is less pronounced than in a period of non-transition elements. As transition elements progress along a series, the nuclear charge increases due to the filling of inner d orbitals, but the effect is mitigated by the shielding of 3d electrons. The shielding is more effective than in non-transition elements, resulting in a more gradual increase in ionization enthalpy. In contrast, non-transition elements experience a sharper increase in ionization enthalpy across a period due to the absence of effective shielding, resulting in a more significant variation along the period.