Questions 2 and 3 refer to the following information and diagrams.
In 1803 John Dalton suggested that each element is made of only one kind of atom. Dalton said that the elements were different because their basic atoms are different, but all atoms of a specific element are identical. By the end of the century, in 1897, Joseph John Thomson proved that the atom was "cuttable." That is, he proved that there were particles smaller than atoms that were part of atoms. Thomson had discovered electrons. Thomson proposed a model of the atom in which negatively charged electrons were distributed throughout a positively charged sphere, a bit like blueberries spread throughout a muffin. Thomson’s model intrigued the scientific community, and other scientists set out to investigate the structure of the atom.
Just over twenty years later, in 1911, Ernest Rutherford, a former student of Thomson’s, presented a different theory of the structure of atoms. Rutherford’s experimental work led him to conclude that nearly all the mass of an atom is concentrated in a tiny nucleus. He also stated that the nucleus is surrounded by electrons traveling at tremendous speeds through the atom’s outer regions. It was as if the nucleus was at the center of a cloud of electrons. Because the atom had no overall electrical charge, Rutherford concluded that the nucleus of an atom had a positive charge.
Questions 4 and 5 refer to the following information and diagrams.
In 1913 Niels Bohr, who had worked with Rutherford, suggested that negatively charged electrons could travel in a certain set of orbits around the nucleus, like planets orbiting around the sun. Each orbit was associated with a specific level of energy. The electrons in larger orbits, that is, farther away from the nucleus, had higher energies.
By 1928 another description of electron arrangement was proposed. The work of Erwin Schrodinger, Wolfgang Pauli, Max Born, and Werner Heisenberg led to the assumption that the electron, although a particle, could behave like a wave. This led to the development of the electron cloud model. As in the Rutherford atom, the nucleus is at the center of an atom. But this model proposes that the nucleus is surrounded by electrons moving in paths like a wavy band of clouds around the nucleus. Each path is associated with a particular level of electron energy.
Questions 6 through 10 refer to the following information.