BJU Physical Science Chapter 3

What is J. J. Thomson’s atomic model called?

• the nuclear model

• the plum pudding model

• the quantum-mechanical model

• the Saturnian model

Which of the following observations did not lead Rutherford to believe that most of the atom’s mass and positive charges were densely packed into a very small space?

• Some alpha particles bounced off the foil at sharp angles.

• Some alpha particles emitted photons as they fell back into their original energy levels.

• Some alpha particles were deflected at varying angles as they passed through the gold foil.

• Most alpha particles passed through the gold foil undeflected.

The Bohr model suggests that electrons move

• in a flat ring around a massive, positively charged center.

• only in distinct, spherical orbits at fixed distances from the nucleus.

• randomly about the nucleus.

• rapidly throughout a uniform, positively charged matrix.

Aristotle first called particles atomos, from which we get our word atom.

• True

• False

John Dalton proposed that atoms are hard spheres of different sizes and masses.

• True

• False

Scientists currently hold to the quantum-mechanical model because it is able to precisely pinpoint the locations of an atom’s electrons.

• True

• False

The __________ is about 1836 times the mass of an electron. The slightly more massive __________ is about 1838 times the mass of an electron.

• cation; anion

• proton; neutron

• anion; cation

• electron; positron

• neutron; proton

Carbon-14 is different from carbon-12 in that it has a different number of __________.

• molecules

• protons

• neutrons

• electrons

• all the above

Which of the following is a weighted average?

• atomic mass

• atomic number

• mass number

• none of the above

Democritus suggested that matter

• could be subdivided an unlimited number of times.

• existed in the form of very small, indivisible particles.

• was continuous.

• was made of hard spherical atoms surrounded by heat envelopes.