Lesson 4.3 Flashcards
is discovered using a cathode-ray tube
Electron
the cathode-ray tube has two charged plates
cathode and anode
an English physicist used the cathode ray tube, and the electromagnetic theory to determine the ratio of electric charge to the mass of the individual negatively charged particle
Joseph John Thomson ( also known as J.J. Thomson)
Some experiments added two electrically charged plates and a magnet to the outside of the cathode ray tube.
ratio of electric charge to the mass of the individual negatively charged particle
If the magnetic field is on and the electric field is off, the cathode ray hit point A.(_)
Upper
If only the electric field is on, the ray hit point C.(_)
Lower
If both the magnetic and the electric fields are off or when they cancel each other’s influence, the ray strikes point B.(_)
Straight middle
Since the cathode ray is attracted to the positively-charged plate and repelled by the negatively-charged plate, it must consist of negatively-charged particles.
This negatively charged particle was called _.
electron
The mass to charge ratio obtained by Sir J.J. Thomson was
1.76 ✕ 10^8 C/g
1.76 ✕ 108 C/g, where C stands for _, the unit of the electrical charge.
coulomb
was able to quantify the charge of the electron in his oil-drop experiment in 1906.
Robert Millikan
In Millikan’s experiment, he used a fine spray of ionized oil.
With electromagnetic force, the droplets suspended in air.
He was able to calculate the charge of the electron and the mass of the electron
The charge of the electron = _
–1.6022 ✕ 10^-19 C
In Millikan’s experiment, he used a fine spray of ionized oil.
With electromagnetic force, the droplets suspended in air.
He was able to calculate the charge of the electron and the mass of the electron
The mass of the electron = _
9.10 ✕ 10^-28 g
During the early 1900s, two features of atoms had become clear.
Atoms contain electrons.
Atoms are electrically neutral.
In order to maintain an electrical neutral atom. It must contain an equal number of positive and negative charges.
The Plum Pudding Model
In 1910, a New Zealand physicist _ _ decided to use alpha particles to probe the structure of the atoms, together with his associate Hans Geiger and an undergraduate named Ernest Maden.
Ernest Rutherford
They observed that the majority of particles penetrated the foil either undeflected or slightly deflected.
Some alpha particles were deflected at a large angle. In some instances, an alpha particle bounced back in the direction of its source.
Most of an atom must be empty space with electrons that allow the majority of the alpha particle to pass through.
On the center of the atom, there is a positively charged dense core (_).
Nucleus
The positively charged particles in the nucleus are called
Proton
In separate experiments, the charge of each proton has the same magnitude as that of electron
–1.6022 ✕ 10^-19 C
In separate experiments, the charge of each proton has the same magnitude as that of electron and that the mass of the proton is _
1.67262 ✕ 10 -24 grams.
The inconsistency on the ratio of the mass hydrogen atom to the mass of helium atoms led Rutherford and the other scientists to speculate that there must be another subatomic particle in the atomic nucleus.
The proof was provided by another English physicist, _ _, in 1932 on his alpha particle and beryllium experiment.
James Chadwick
Later experiments revealed that the rays consisted of electrically neutral particles having a mass slightly greater than that of protons.
Chadwick names these particles, as _
Neutrons
An atom has an electron, proton, and neutron. Protons and neutrons are packed in an extremely small nucleus and carries the bulk of the mass of an atom, while the electrons occupy the space around the nucleus providing volume to the atom.
proposed that the electron move in orbits around the nucleus
Planetary Model
Neils Bohr
proposed that electrons do not move in a set of paths around the nucleus but in waves
impossible to locate electrons, cloud of probability
Electron Cloud Model
The three subatomic particles of an atom are electron, proton, and neutron.
The electron was discovered by J.J. Thomson using a cathode ray experiment, while Robert Millikan calculated the charge and mass of the electron through his oil-drop experiment.
The nucleus and proton was discovered by Ernest Rutherford and his associates through the gold foil experiment.
The neutron was discovered by James Chadwick through his alpha particle and beryllium experiment.
