In 1897, Joseph Thomson discovered that atoms contained electrons. He proposed a change in the atomic theory of that time, and the theory was modified because of his discovery. Since Thomson’s discovery, atomic theory has been further modified. What is the best explanation for why scientific theories are modified?Group of answer choicesNew evidence that supports a change prompts scientists to modify earlier theories.Scientists want to prove that the work of other scientists is wrong.So much information is available today that it is harder to focus research and disprove theories.Theories more than ten years old are usually out of date.

Prior to Thomson's discovery, the atom was thought to be indivisible. Explain the significance of Thomson's concept of the electron.

Why did the model of the atom change?A.Experiments provided new evidence about the atom.B.The structure of atoms changed over time.C.New materials became available to build better models.D.Scientists did not like the original model.

Identify the scientist who rejected Thomson’s atomic model.

What important discovery did Ernest Rutherford make?A.He found that light could make electrons flow in metals.B.He found that electrons were negatively charged particles.C.He found that the atom contained both protons and electrons.D.He found that the atom was made up of mostly empty space.

How did the Bohr model of the atom affect scientific thought?A.Scientists accepted the model at first, but later rejected it.B.Scientists rejected the model because it didn't fit the data.C.Scientists accepted Bohr's model as a useful explanation.D.Scientists finally agreed that Bohr's model was accurate.