The error message is correct, but that is a different error. You have apparently 6 atom types, but there are only 5 element to type mappings. Again, this is all documented. You just need to read the documentation with significantly more care and specifically the parts related to hybrid styles.
On a hunch, I checked the archives and have to remind you of this post by @srtee. It is rarely a good idea to use a hybrid pair style with ReaxFF, but this one seems particularly bad. A large part of the interactions of polar molecules with metal surfaces is the polarization of the metal (for an ideally polarizable metal, the induced charges are of the same magnitude but opposite sign as the original charges). With an ionic liquid, this is particularly large, yet by using you setup, you only have a mechanical coupling (i.e. no polarization at all) and not even the embedding term of the copper is correct since the contribution from the molecules at the surface are not considered.
In summary, you need more help than a forum can provide and at a much more fundamental level. Both in how to use a software correctly and follow its documentation and in how to set up complex simulations and in understanding the models that you are using within the simulation.
The hybrid pair style in LAMMPS can be a very powerful and useful tool, but like many other powerful tools, it needs to be used with care and consideration.