Why 1st ionisation enthalpy of copper is more than sodium
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Cu has configuration as [Ar] 3d10 4s1 whereas Na has [Ne] 3s1. Due to the poor shielding effect of d-orbital in copper the s - electron feels high nuclear effective charge than s-elactron in sodium. Thus, more energy is neede to remove electron from s-orbital of copper than sodium which results in higher 1st ionisation enthalpy of Cu than Na.
Cu has configuration as [Ar] 3d10 4s1 whereas Na has [Ne] 3s1. Due to the poor shielding effect of d-orbital in copper the s - electron feels high nuclear effective charge than s-elactron in sodium. Thus, more energy is neede to remove electron from s-orbital of copper than sodium which results in higher 1st ionisation enthalpy of Cu than Na.