A. James Chadwick, 1932, by bombarding beryllium with alpha particles
8.
What is a neutron and what are its properties?
A.
A neutron is found orbiting the nucleus like electrons but in a different path
B.
A neutron carries a positive charge equal and opposite to an electron
C.
A neutron is an electrically neutral (uncharged) sub-atomic particle present in the nucleus of all atoms except ordinary hydrogen; its mass is approximately equal to that of a proton
D.
A neutron is formed by combining an electron and a proton
C. A neutron is an electrically neutral (uncharged) sub-atomic particle present in the nucleus of all atoms except ordinary hydrogen; its mass is approximately equal to that of a proton
9.
J.J. Thomson proposed the first model of the atom. Which of the following correctly describes Thomson's model?
A.
An atom is a sphere of uniform positive charge with electrons embedded in it like raisins in a pudding (plum pudding model)
B.
An atom has electrons arranged in definite shells or orbits of specific energy
C.
An atom has a tiny, dense positive nucleus surrounded by electrons revolving in circular orbits
D.
An atom is made up of only positive charges with neutrons distributed uniformly
A. An atom is a sphere of uniform positive charge with electrons embedded in it like raisins in a pudding (plum pudding model)
10.
Thomson's model explained the electrical neutrality of the atom. How?
A.
The protons and neutrons balance the electrons by equal but opposite forces
B.
The positive charge of the sphere and the negative charge of the embedded electrons are equal in magnitude, so they cancel each other, making the atom neutral
C.
All charges flow out of the atom, leaving it neutral
D.
The positively charged sphere repels the electrons, keeping them outside and balancing charges
B. The positive charge of the sphere and the negative charge of the embedded electrons are equal in magnitude, so they cancel each other, making the atom neutral
11.
What are the LIMITATIONS of Thomson's Model of the atom?
A.
It was abandoned because protons were not yet discovered when it was proposed
B.
It failed only because it could not explain the mass of atoms
C.
It failed to explain the results of Rutherford's alpha-particle scattering experiment; it did not account for the nucleus; it could not explain atomic spectra
D.
It correctly explained Rutherford's scattering experiment
C. It failed to explain the results of Rutherford's alpha-particle scattering experiment; it did not account for the nucleus; it could not explain atomic spectra
12.
Rutherford's famous alpha-particle scattering experiment used which metal foil?
A.
Gold foil (a very thin sheet of gold, approximately 1000 atoms thick)
