The ancient Greeks developed a concept of matter that stated that all matter was composed of very small indivisible particles called

• protons

• elements

• electrons

• atoms

Using a Cathode Ray Tube with deflecting plates, J.J. Thomson discovered a fundamental subatomic particle called a(n)

• proton

• neutron

• electron

• ion

The fundamental charge of an electron was discovered by

• J.J. Thomson

• Robert Millikan

• Ernest Rutherford

• Niels Bohr

Rutherford studied the nature of matter by investigating how alpha particles interacted with thin gold foil. He discovered that

• nearly all of the alpha particles passed through the foil undeflected.

• some alpha particles were widely deflected and even were scattered backwards by the nuclei of the atoms in the foil.

• most of the mass of an atom is concentrated in the nucleus.

• all of the above are true.

The number of protons in an atom is called the

• atomic number

• atomic weight

• mass number

• isotope number

Isotopes of an element have

• different number of protons but the same number of neutrons.

• the same number of protons and neutrons.

• the same number of protons but different number of neutrons.

• the same atomic weight.

Uranium, ^235U, has

• 92 protons, 143 neutrons, and 92 electrons.

• 235 protons, 92 electrons and 143 electrons.

• 143 protons, 235 neutrons, and 143 electrons.

• 143 protons, 143 neutrons and 92 electrons.

Which of the following statements does NOT describe Bohr’s model of the atom?

• Electrons can be located anywhere within the atom outside of the nucleus.

• Electrons in a given orbit do not emit radiation.

• Electrons must “leap” from orbit to orbit.

• Electrons can be treated as particles.

Compare the quantum mechanics model of the atom to the Bohr model of the atom.

• Quantum mechanics considers the wave behavior of the electron while the Bohr model considers the particle nature of the electron.

• As long as electrons remain in its orbit it emits no radiation.

• The location of the particle is known in the Bohr model. In the quantum mechanics model, the electrons position is defined in probability terms.

• The Bohr model could not be used for larger atoms.

• All of the above statements are valid.

How much energy must an electron absorb to jump from level n = 1 to level n = 3?

• 1.51 eV

• 12.1 eV

• 13.6 eV

• 15.1 eV

• Electrons cannot jump two levels at once.