Chapter 14 Review

Video Review

Key Concept Summary

TA Summary

Vocabulary

Dense, positively-charged center of the atom.

Rutherford Model.

Spectra in which only certain specific colors are present.

Thomson Model.

Positively charged particle emitted by some radioactive materials (a helium nucleus).

True/False

The electron has no mass.

True False

The red photons found in the emission spectrum of atomic hydrogen are less energetic than the violet photons.

True False

The rare, backward reflection of alpha particles convinced Rutherford that the atom consisted of a dense, positively-charged nucleus.

True False

In gas discharge tube experiments, positive fragments from different types of atoms are similar to one another.

True False

To explain the continuous spectrum of hot objects, Planck proposed that light could only be absorbed or emitted in discrete amounts.

True False

Bohr failed to explain why an accelerated electron does not radiate energy.

True False

Rutherford fully expected alpha particles to bounce off of the gold foil.

True False

The nucleus of an atom occupies more than half of the atom's volume.

True False

The color of a hot object is related to its temperature.

True False

Analysis

Thompson's gas discharge experiments provide direct experimental evidence for the

Exclusion Principle Nuclear Model of atoms Bohr model of atoms idea that all atoms are made of charged particles idea that electrons in atoms behave as waves

In the Thomson (plum pudding) model of the atom, an atom is described as

a neutral "pudding" with small lumps of positive and negative charge distributed throughout. a positive "pudding" with small lumps of negative charge distributed throughout a negative "pudding" with small lumps of positive charge distributed throughout a negative "pudding" with one large lump of positive charge in the middle. a neutral "pudding" with lumps of negative charge around the outside and lumps of positive charge in the middle.

In what model do electrons orbit the nucleus so that any orbit allowed by Newtonian physics can be occupied by an electron? (i.e., there are no restrictions on allowed electron energies.)

quantum model Thomson or "plum pudding" Rutherford or "solar system" model Bohr or "modified solar system" model the molecular model

White light (containing all visible colors) passes through a gas that absorbs some of the light. The spectrum of light that passes through the gas is then analyzed. That spectrum could best be described as

continuous a discrete spectrum of colored lines. a mostly continuous spectrum that is missing some colors. a discrete black lines in the spectrum that correspond to the absorbed light. a completely black spectrum.

Gases emit light when they are energized by an electrical discharge. The light results when an electron

"jumps" from one energy level up to a higher energy level. "jumps" from one energy level down to a lower energy level. is completely removed from the atom. is absorbed by the nucleus.

Which of the following models of the atom is correct?

Thompson Rutherford Bohr None of the above

What determines the color of the lines in an atomic emission spectrum?

The electron's velocity in orbiting the atom. The difference in energies of the atom's energy levels. The voltage used to excite the atoms. The number of electrons around the atom.

Hydrogen has one electron. Why does its emission spectrum have four lines?

The atom has four energy levels. The electron can be deflected through four different angles. The electron absorbs all four colors at once, so it emits more than one photon. One electron will only emit one photon at a time. Since there are lots of atoms in a tube of gas, there are lots of electrons emitting photons.

An electron has a charge of 1.6×10^-19 C. Can you cut an electron in half and get a particle with charge 0.8×10^-19 C?

No No, you can't cut an electron in half, but yes you can get a charge of 0.8×10^-19 C by transferring half of the charge to another particle. Yes you can cut an electron in half, but all of the charge will be on one half or the other, so you will never get a charge of 0.8×10^-19. Yes

The oil drop experiment measured:

electron charge electron mass electron size all of the above

Which experiment demonstrated that atoms were made up of positive and negative pieces?

cathode ray tubes the Thompson experiment the oil drop experiment the Rutherford scattering experiment

Which model of the atom pictured electrons as orbiting the atom's nucleus like planets orbit the sun?

Thompson Rutherford Bohr all three

Does the Bohr model of the atom accurately predict atomic emission spectra?

Yes for all atoms No Yes for atoms with one electron, but no for all other atoms.

According to the Bohr model of the atom, how many energy levels does a hydrogen atom have?

one four one occupied and four excited states one occupied and an infinite number of excited states.

If an excited hydrogen atom has its electron in the 3rd energy level, what will happen?

The electron will fall back down to the ground state emitting one photon. The electron will fall to the second, then first emitting two photons. either a or b. either a or b, or it could just sit there, electrons can be in any allowed energy level.

Free Response

What role did Rydberg’s formula play in the development of Bohr’s model?
Use a qualitative (no numbers needed) timeline to map out the sequence of events (experiments) and models that led to the Bohr model.
Use the laws of force and motion to explain Rutherford’s hypothesis (alpha particles would travel in either straight lines or experience small deflections on passing through the gold foil) based on the Plum Pudding Model. Use these same laws to explain why the results of the gold foil experiments ruled out this hypothesis and required the existence of a dense, small, positively-charged nucleus. (It is the logic of Rutherford’s arguments that we are most interested in. You need not give equations.)
How can a continuous spectrum be made up from discrete amounts of energy? What role does the size of Planck’s constant h play in your answer?
What is the relationship between the frequencies present in an emission spectrum and those missing in an absorption spectrum? What law(s) require that there be this type of correspondence?
The absorption spectrum at the bottom of this figure was obtained from an unknown material in the gas discharge tube. Compare the absorption spectrum with the known emission spectra for sodium, mercury, and neon gases and identify the unknown specimen.