Name: ______Date: ______
Section 4.2 – Atomic Structure
Structure of the Nuclear Atom
Cathode-ray tubes are found in ______, computer monitors, and many other devices with ______displays.
Subatomic Particles
What are three kinds of subatomic particles?
Subatomic Particles
Three kinds of subatomic particles are ______, ______, and ______.
Subatomic Particles
Electrons
In 1897, the English physicist ______(1856–1940) discovered the electron.
Electrons are ______charged subatomic particles.
Subatomic Particles
Thomson performed experiments that involved passing electric current through gases at low pressure.
The result was a glowing beam, or cathode ray, that traveled from the cathode to the anode.
Subatomic Particles
A cathode ray is deflected by a ______.
Since magnets only have an affect on ______, cathode rays had to be made of some ______.
Subatomic Particles
A cathode ray is deflected by electrically ______plates.
Cathode rays must have an electric charge.
- ______charge
Since the same thing happened regardless of the type of metal used for the cathode and anodes, Thomson said that ______rays were part of all matter and named them ______.
Subatomic Particles
Protons and Neutrons
· In 1886, ______(1850–1930) observed a cathode-ray tube and found rays traveling in the direction opposite to that of the cathode rays. He concluded that they were composed of ______particles.
o Such positively charged subatomic particles are called ______.
· In 1932, the English physicist ______(1891–1974) confirmed the existence of yet another subatomic particle: the ______.
o Neutrons are subatomic particles with ______but with a mass nearly ______to that of a proton.
Subatomic Particles
Table 4.1 summarizes the properties of electrons, protons, and neutrons.
The Atomic Nucleus
J.J. Thompson and others supposed the atom was filled with ______charged material and the electrons were ______distributed throughout.
This model of the atom turned out to be short-lived, however, due to the work of ______(1871–1937).
The Atomic Nucleus
Rutherford’s Gold-Foil Experiment
In 1911, Rutherford and his coworkers at the University of Manchester, England, directed a narrow beam of ______particles at a very thin sheet of ______foil.
The Atomic Nucleus
Alpha particles ______from the gold foil.
The Atomic Nucleus
The Rutherford Atomic Model
Rutherford concluded:
· The atom is mostly ______.
· All the positive charge and almost all of the ______are concentrated in a small region called the ______.
· The nucleus is the tiny ______of an atom and is composed of ______and ______.
The Atomic Nucleus
In the nuclear atom:
· The protons and neutrons are located in the ______.
· The electrons are ______around the nucleus and occupy almost all the ______of the atom.