Are the angles between lead and sulfur atoms 90 degrees?

No, the angles between lead and sulfur atoms are not typically 90 degrees. In lead sulfide (PbS), the structure is generally octahedral, with the lead atoms coordinated to sulfur atoms in a way that results in bond angles that are closer to 180 degrees. The exact angles can vary depending on the specific structure and coordination environment, but they do not conform to a rigid 90-degree angle.