Atoms and the Periodic Table

What did Bohr’s model of the atom include that Rutherford’s model did not have?

• A nucleus

• energy levels

• electron clouds

• smaller particles

Which statement describes one feature of Rutherford’s model of the atom?

• The atom is mostly empty space

• The atom cannot be divided into smaller particles

• Electron clouds are regions where electrons are likely to be found

• The electrons are located within the positive material of the nucleus.

Why did Thomson’s results from experimenting with cathode rays cause a big change in scientific thought about atoms?

• His results gave people a picture of what atoms look like for the first time.

• His results gave the first clues that atoms could be created and destroyed.

• His results gave the first experimental evidence that matter is made up of atoms.

• His results gave the first evidence that atoms were made up of smaller particles.

The charged particles in the beams that Thomson studied came from atoms. As these particles moved away from their original atoms, they formed a visible beam. The current model of the atom includes protons, neutrons, and electrons.

What is the best use of an atomic model to explain the charge of the particles in Thomson’s beams?

• An atom’s negative particles are surrounded by positive matter, so the positive particles are easier to remove.

• An atom’s positive particles are surrounded by negative matter, so the negative particles are easier to remove.

• An atom’s smaller negative particles are at a distance from the central positive particles, so the negative particles are easier to remove.

• An atom’s larger positive particles are at a distance from the central negative particles, so the positive particles are easier to remove.

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The plum pudding model of the atom states that

• each atom has an overall negative charge.

• each atom has a dense, positively charged center.

• an atom is a solid, indivisible sphere that makes up all matter.

• an atom is made up of electrons in a sea of positive charges.

Oppositely charged objects attract each other. This attraction holds electrons in atoms and holds atoms to one another in many compounds. However, Ernest Rutherford’s model of the atom failed to explain why electrons were not pulled into the atomic nucleus by this attraction.

What change to the atomic model helped solve the problem seen in Rutherford’s model?

• Bohr’s work with atomic spectra led him to say that the electrons were limited to existing in certain energy levels, like standing on the rungs of a ladder.

• Bohr’s work with cathode rays led him to say that the electrons were located within the mass of positive material, like plums in a pudding.

• Thomson’s work with cathode rays led him to say that the electrons were located within the mass of positive material, like plums in a pudding.

• Thomson’s work with atomic spectra led him to say that the electrons were limited to existing in certain energy levels, like standing on the rungs of a ladder.

Scientists have changed the model of the atom as they have gathered new evidence. One of the atomic models is shown below.

What experimental evidence led to the development of this atomic model from the one before it?

• A few of the positive particles aimed at a gold foil seemed to bounce back.

• The colors of light emitted from heated atoms had very specific energies.

• Equations were used to identify regions around the nucleus where electrons would likely be.

• Cathode rays were bent in the same way whenever a magnet was brought near them.

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Which statement belongs to Dalton’s atomic theory?

• Atoms have a massive, positively charged center

• Atoms cannot be created or destroyed.

• Atoms can be broken down into smaller pieces.

• Electrons are located in energy levels outside of the nucleus.

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A cathode ray tube is made of glass with a small amount of some kind of gas in it. It has metal electrodes at each end to pick up an electric current. The electrodes are named "positive” and "negative,” which were words used by Benjamin Franklin in the 1700s to describe electricity. A bright ray forms in the gas when an electric current is applied to metal electrodes. In the 1800s, an important scientist suspected that the negatively charged particles in a cathode ray were present in all atoms.

What procedure would allow that scientist to investigate this idea?

• observing if the cathode ray forms when the electric current is off

• making cathode ray tubes out of different materials to see if the ray is the same

• using different magnets to see if the cathode ray responds in the same way to each

• changing the strength of the electric current and observe how the ray forms and changes

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Which scientist developed the first model of the atom that showed the structure of the inside of an atom?

• Dalton

• Bohr

• Rutherford

• Thomson