How many electrons are in the highest energy orbital of the element copper?

Explanation:

According to the Aufbau principle, in the ground state of an atom or ion the electrons fill atomic orbitals of the lowest energy levels first, before filling the higher energy levels.

For example, atomic number of copper is 29 and its electronic configuration is

So, in copper the 4s energy shell is filled first because it has less energy as compared to 3d shell.

And, after filling of 4s orbital there occurs filling of 3d orbital. Since, there are 10 electrons in a 3d orbital of copper.

Thus, we can conclude that the highest energy orbital of the element copper contains 10 electrons.

the answer would be c

the answer is option a.