History and Experiments with Electrons - AP Chemistry

Ernest Rutherford made great advances in current understanding of atomic structure through his gold foil experiment. When firing positively-charged alpha particles at a thin film of gold atoms, most particles were found to pass straight through the film with little to no deflection, indicating that atoms were mostly composed of empty space. A few particles were deflected at large angles, indicating direct collisions with the positively charged nuclei of the atoms.

In the Rutherford experiment, a beam of alpha particles was shot through a gold foil, with most of the particles flying straight through and a few scattering at angles greater than . These results suggest that most of the volume of foil was "empty" space, with small concentrations of positive charge, which we now know is the nucleus.

de Broglie suggested that all matter has both wave-like and particle-like properties. His
equation states that λ= h/mv , where λ is the wavelength, m is mass, h is Planck’s constant,
and v is velocity. 4 mph is 1.8 m s−1 and Planck’s constant is 6.626e-34 kg m2 s−1 , giving
us a wavelength (λ) 4.6e-36 m ! A very small wavelength, indeed.

Rutherfords experiment focused a beam of alpha particles on a piece of gold foil. The result showed that most of the alpha particles passed through the foil, while a small fraction of particles were significantly deflected. This suggested the presence of a small, dense, positively charged nucleus. Most of the alpha particles passed through the electron clouds of the gold atoms, without impacting the nuclei, while those that did impact the nuclei were deflected by the positive charge of the nucleus.

Rutherford's experiment does not give us any concrete information about neutrons, nor does it allow us to assume that the number of protons and neutrons in the nucleus are equal.

Recall that J.J. Thomson conducted the cathode ray tube experiment that proved the existence of a small negatively charged particle. Thomson was also able to determine the charge-to-mass ratio of an electron. Robert Millikan is the scientist who conducted the oil drop experiment, from which he was able to find the charge of the electron and deduce its mass using the electron's charge-to-mass ratio. Dalton was not involved in the discovery of the electron.

All the oil drops must have a charge that is a multiple of . If an oil drop is observed to have a charge of , that means the oil drop has three electrons. If an oil drop is observed to have a charge of , that means the oil drop has twelve electrons. If an oil drop is observed to have a charge of , that means the oil drop has two electrons.

To find the number of electrons this oil drop contains, divide the observed charge by the charge of a single electron.

This oil drop contains electrons.

Recall that J.J. Thomson conducted the cathode ray tube experiment that proved the existence of a small negatively charged particle. Thomson was also able to determine the charge-to-mass ratio of an electron. Robert Millikan is the scientist who conducted the oil drop experiment, from which he was able to find the charge of the electron and deduce its mass using the electron's charge-to-mass ratio.

From the cathode ray tube experiment, J.J. Thomson was only able to prove the existence of the negatively charged electron. From the results of the experiment, he also postulated that an atom was made up of a large spherical cloud of positive charge with negatively charged electrons embedded within. This model is also known as the plum pudding model.

Ernest Rutherford made great advances in current understanding of atomic structure through his gold foil experiment. When firing positively-charged alpha particles at a thin film of gold atoms, most particles were found to pass straight through the film with little to no deflection, indicating that atoms were mostly composed of empty space. A few particles were deflected at large angles, indicating direct collisions with the positively charged nuclei of the atoms.

In the Rutherford experiment, a beam of alpha particles was shot through a gold foil, with most of the particles flying straight through and a few scattering at angles greater than . These results suggest that most of the volume of foil was "empty" space, with small concentrations of positive charge, which we now know is the nucleus.

de Broglie suggested that all matter has both wave-like and particle-like properties. His
equation states that λ= h/mv , where λ is the wavelength, m is mass, h is Planck’s constant,
and v is velocity. 4 mph is 1.8 m s−1 and Planck’s constant is 6.626e-34 kg m2 s−1 , giving
us a wavelength (λ) 4.6e-36 m ! A very small wavelength, indeed.

Rutherfords experiment focused a beam of alpha particles on a piece of gold foil. The result showed that most of the alpha particles passed through the foil, while a small fraction of particles were significantly deflected. This suggested the presence of a small, dense, positively charged nucleus. Most of the alpha particles passed through the electron clouds of the gold atoms, without impacting the nuclei, while those that did impact the nuclei were deflected by the positive charge of the nucleus.

Rutherford's experiment does not give us any concrete information about neutrons, nor does it allow us to assume that the number of protons and neutrons in the nucleus are equal.

Recall that J.J. Thomson conducted the cathode ray tube experiment that proved the existence of a small negatively charged particle. Thomson was also able to determine the charge-to-mass ratio of an electron. Robert Millikan is the scientist who conducted the oil drop experiment, from which he was able to find the charge of the electron and deduce its mass using the electron's charge-to-mass ratio. Dalton was not involved in the discovery of the electron.

All the oil drops must have a charge that is a multiple of . If an oil drop is observed to have a charge of , that means the oil drop has three electrons. If an oil drop is observed to have a charge of , that means the oil drop has twelve electrons. If an oil drop is observed to have a charge of , that means the oil drop has two electrons.

To find the number of electrons this oil drop contains, divide the observed charge by the charge of a single electron.

This oil drop contains electrons.

Recall that J.J. Thomson conducted the cathode ray tube experiment that proved the existence of a small negatively charged particle. Thomson was also able to determine the charge-to-mass ratio of an electron. Robert Millikan is the scientist who conducted the oil drop experiment, from which he was able to find the charge of the electron and deduce its mass using the electron's charge-to-mass ratio.

From the cathode ray tube experiment, J.J. Thomson was only able to prove the existence of the negatively charged electron. From the results of the experiment, he also postulated that an atom was made up of a large spherical cloud of positive charge with negatively charged electrons embedded within. This model is also known as the plum pudding model.

Ernest Rutherford made great advances in current understanding of atomic structure through his gold foil experiment. When firing positively-charged alpha particles at a thin film of gold atoms, most particles were found to pass straight through the film with little to no deflection, indicating that atoms were mostly composed of empty space. A few particles were deflected at large angles, indicating direct collisions with the positively charged nuclei of the atoms.

In the Rutherford experiment, a beam of alpha particles was shot through a gold foil, with most of the particles flying straight through and a few scattering at angles greater than . These results suggest that most of the volume of foil was "empty" space, with small concentrations of positive charge, which we now know is the nucleus.