Our understanding of the atom has changed over time. Which idea that was once accepted is now considered scientifically inaccurate?

A. Electrons are arranged in layers.

B. An atom is a solid sphere.

C. The nucleus is the center of the atom.

D. Electrons have a negative charge.

B. An atom is a solid sphere

Explanation:

The idea that the atom was a solid sphere paved back to the first atomic model in the 19th century theorized by John Dalton. According to him, an atom is intact and hard and cannot be broken down or divided.

However, many scientists continued to research and it was found that the atom was not actually a solid sphere. It was made up of protons (positively-charged), electrons (negatively-charged) and neutrons (neutrally-charged). This invalidated Dalton's solid sphere model.