Ideas of the atom have changed over time.
which idea do scientists now consider inaccurate?
electrons are arranged in layers.
electrons have a negative charge.
the nucleus is the center of the atom.
an atom is solid material.

The idea about the atom which has now been dropped off as inaccurate by the scientist is the idea of the atom to be a solid material.

Option D

Explanation:

From Rutherford Alpha Ray scattering Experiment, most of the atom spaces are empty because the alpha particles are not deviated by positive charge of nucleus. This leads to the conclusion that atoms cannot be considered as perfect solid sphere.

Apart from the last option, all other options are still found to be accurate. That is, electrons are found in layers which are known as the electron shells. The electrons do have the negative charge which is neutralized by the positive charge of the nucleus. And nucleus is present in the center.