What is the equation of Enthalpy of Atomisation of Copper ?

The standard of atomization, ##DeltaH_"atom"^@##, for atoms is just for the process of converting however many ##"mol"##s of the standard state (i.e. at ##25^@ "C"## and ##"1 atm"##) of the element needed to make ##"1 mol"## of its gaseous form.

Thus the ##DeltaH_"atom"^@## of ##"Cl"_2(g)## to ##"Cl"(g)## is for this reaction, for instance:

##1/2"Cl"_2(g) -> "Cl"(g)##

which is really half the enthalpy of breaking the ##"Cl"-"Cl"## bond of ##"1 mol"## of ##"Cl"_2(g)## molecules, at ##25^@ "C"## and ##"1 atm"##.

For ##"Cu"(s)##, which is a transition metal, its ##DeltaH_"atom"^@## is based on the reaction:

##"Cu"(s) stackrel(Delta" ")(->) "Cu"(g)##

which in this case is really the enthalpy of sublimation for copper solid, at ##25^@ "C"## and ##"1 atm"##.