Chapter 11: Modern Atomic Theory

Question 1

Light (electromagnetic radiation) travels as ________.

Answer 1

Light (electromagnetic radiation) travels as waves.

Question 2

Energy can be transmitted from one place to another by ______________________.

Answer 2

Energy can be transmitted from one place to another by light - more properly called electromagnetic radiation.

Question 3

Electromagnetic Radiation

Answer 3

Radiant energy that exhibits wavelike behavior and travels through space at the speed of light in a vacuum.

Question 4

What are the three properties of a wave?

Answer 4

1. Wavelength
2. Frequency
3. Speed

Question 5

wavelength

Answer 5

The wavelength (symbolized by the Greek letter lambda, 𝛌) is the distance between two consecutive peaks or troughs in a wave.

Question 6

frequency

Answer 6

The frequency of a wave (symbolized by the Greek letter nu, 𝝂) indicates the number of waves, or cycles, per second that pass a given point in space.

Question 7

speed (of a wave)

Answer 7

The speed of a wave indicates how fast a given peak travels through the water.

Question 8

The various types of electromagnetic radiation (X-rays, microwaves, etc.) differ in their _____________.

Answer 8

The various types of electromagnetic radiation (X-rays, microwaves, etc.) differ in their wavelengths.

Question 9

Radiation provides an important means of ____________.

Answer 9

Radiation provides an important means of energy transfer.

For example, the energy from the sun reaches the earth mainly in the forms of visible and ultraviolet radiation. The glowing coals of a fireplace transmit heat energy by infrared radiation. In a microwave oven, the water molecules in food absorb microwave radiation, which increases their motions; this energy is then transferred to other types of molecules by collisions, increasing the food’s temperature.

Question 10

Electromagnetic radiation (“light”) moves in __________ as it carries __________ through space.

Answer 10

Electromagnetic radiation (“light”) moves in waves as it carries energy through space.

Question 11

Electromagnetic radiation sometimes has properties that are characteristic of ___________.

Answer 11

Electromagnetic radiation sometimes has properties that are characteristic of particles.

Question 12

photons

Answer 12

“particles” of electromagnetic radiation

Question 13

One way to think of a beam of light traveling through space is as ___________________________ called photons.

Answer 13

One way to think of a beam of light traveling through space is as a stream of tiny packets of energy called photons​.

Question 14

What is the exact nature of light? Does it consist of waves or is it a stream of particles of energy?

Answer 14

It seems to be both.

Question 15

Describe light’s “Wave-Particle Nature”.

Answer 15

Electromagnetic radiation (a beam of light) can be pictured in two ways: as a wave and as a stream of individual packets of energy called photons.

Question 16

Different wavelengths of electromagneti radiation carry different amounts of ___________.

Answer 16

Different wavelengths of electromagneti radiation carry different amounts of energy.

Question 17

In general, the longer the wavelength of light, the __________ the energy of its __________.

Answer 17

In general, the longer the wavelength of light, the lower the energy of its photons.

Question 18

Explain what is meant by the term “excited state” as it applies to an electron.

Answer 18

An atom with excess energy is said to be in an excited state. An excited atom can release some or all of its excess energy by emitting a photon (a “particle” of electromagnetic radiation) and thus move to a lower energy state.

In other words, when atoms receive energy from some source, they become excited (meaning they possess excess energy). They can then release this energy by emitting light, and this emitted energy is carried away by a photon. Thus, the energy of the photon corresponds exactly to the energy change experienced by the emitting atom.

• High-energy photons correspond to short-wavelength light, and low-energy photons correspond to long-wavelength light.
• The photons of red light therefore carry less energy than the photons of blue light because red light has a longer wavelength than blue light does.

Question 19

Is an electron in an excited state higher or lower in energy than an electron in the ground state?

Answer 19

The lowest possible energy state of an atom is called its ground state.

Question 20

Is an electron in an excited state more or less stable than an electron in the ground state?

Question 21

An important point to remember about an atom’s various energy states is that the energy contained in the photon correponds to the ________________________________________.

Answer 21

An important point to remember about an atom’s various energy states is that the energy contained in the photon correponds to the change in energy that the atom experiences in going from the excited state to the lower state.

Question 22

Why do we only see certain colors when studying the photons of visible light?

Answer 22

We only see certain colors, because only certain types of photons are produced.

Question 23

What do the certain colors, emitted by an excited atom, suggest about that atom and its energy state?

Answer 23

Because only certain photons are emitted, we know that only certain energy changes are occuring. This means that an atom must ahve certain discrete energy levels.

For example, excited hydrogen atoms always emit photons with the same discrete colors (wavelengths), and they never emit photons with energies (colors) in between. So, we can conclude that all hydrogen atoms have the same set of discrete energy levels.

Question 24

Quantized Energy Levels

Answer 24

Energy levels were only certain values are allowed.

Question 25

The energy levels of _____ (none/some/50-50/all) atoms are quantized.

Answer 25

The energy levels of all atoms are quantized.

Question 26

The Bohr Model of the Atom

Answer 26

• The Bohr model assumed electrons travel around the nucleus in circular orbits, which is incorrect.
• Believed the atom could be pictured as a small positive nucleus with electrons orbiting around it.
• Bohr’s model of the hydrogen atom had quantized energy levels that agreed with the hydrogen emission results seen in its emitted photons.
• Bohr pictured the electron moving in circular orbits corresponding to the various allowed energy levels. He suggested that the electron could jump to a different orbit by absorbing or emitting a photon of light with exactly the correct energy content.

Question 27

Electrons (do/do not) move around the nucleus in circular orbits like planets orbiting the sun.

Answer 27

Electrons do not move around the nucleus in circular orbits like planets orbiting the sun.

Surprisingly, we still do not know exactly how the electrons move in an atom.

Question 28

What is the basis behind the Wave Mechanical Model of the Atom?

Answer 28

Louis Victor de Broglie and Erwin Schrödinger suggested that because light seems to have both wave and particle charcteristics (it behaves simultaneously as a wave and as a stream of particles), the electron might also exhibit both of these characteristics.