2A2 Atomic Spectra and Electron Energy

Question 1

Define:

Ground state

Answer 1

The lowest energy configuration of its electrons.

Atoms are most stable in the ground state.

Question 2

Define:

Electron energy level

Answer 2

The specific energy state an electron can occupy in an atom, determined by its distance from the nucleus.

Each electron naturally occupies the lowest available energy level (ground state, n = 1) unless it absorbs energy and transitions to an excited state (n > 1).

Question 3

What is the principal quantum number?

Answer 3

It indicates the main energy level of an electron in an atom, determining its average distance from the nucleus.

The principal quantum number (n) starts at 1, with higher values (n = 2, 3, etc.) indicating electrons in higher energy levels.

Question 4

Who proposed the Bohr model of the atom?

Answer 4

Niels Bohr

in 1913

The Bohr model introduced the concept of quantized energy levels, explaining why electrons occupy specific orbits instead of moving freely.

Question 5

Fill in the blank:

When an electron moves to a higher energy level, it is in an _______ state.

Answer 5

excited

An electron absorbs energy to move to an excited state, temporarily occupying a higher energy level before returning to its ground state.

Question 6

What distinguishes the valence shell in an atom?

Answer 6

It is the outermost electron shell of an atom, containing electrons with the highest energy that participate in chemical bonding.

Electrons in the valence shell are called valence electrons.

Question 7

True or false:

Electrons can transition to any energy level without restriction.

Answer 7

False

Electrons can only transition between quantized energy levels by absorbing or emitting specific amounts of energy, as described by quantum mechanics.

Question 8

What happens when an electron returns to its ground state?

Answer 8

It emits energy as light or another form of radiation.

The ground state is the lowest energy level an electron can occupy, where it is most stable.

Question 9

What factor determines the wavelength of light emitted when an electron transitions between energy levels?

Answer 9

The energy difference between the two initial and final energy levels.

A larger energy difference results in a shorter wavelength (higher frequency), such as ultraviolet (UV) light, while a smaller energy difference produces longer wavelengths like infrared (IR) light.

Question 10

Explain why electrons do not stay in excited states for long.

Answer 10

They lose energy quickly and return to lower energy levels.

This process stabilizes the atom.

Question 11

Why are emission spectra also called bright-line spectra?

Answer 11

Because they appear as distinct bright lines against a dark background due to specific electron transitions releasing quantized energy.

Each bright line corresponds to a specific electron transition, with its wavelength determined by the energy difference between levels.

Question 12

How do electron transitions produce the bright-line spectra of elements?

Answer 12

Each bright line corresponds to a specific electron transition.

These lines are unique for each element, like a spectral fingerprint, and occur when an electron moves from a higher to a lower energy level, emitting light at a precise wavelength.

Question 13

True or false:

Electrons can move between energy levels without absorbing or emitting energy.

Answer 13

False

Energy must be absorbed or released for a transition to occur.

Question 14

What happens when an electron absorbs a photon?

Answer 14

It can be excited to a higher energy level.

The photon must have the right energy for this to occur.

Question 15

Fill in the blank:

When an electron transitions from a higher to a lower energy level, it releases a _______.

Answer 15

photon

The energy of the emitted photon exactly equals the energy difference between the two levels, following the equation E = hƒ (Planck’s equation)

Question 16

What type of energy is typically involved in electron transitions?

Answer 16

Electromagnetic energy, such as light or photons.

The energy of emitted or absorbed photons corresponds to specific wavelengths in the atomic emission or absorption spectrum, forming unique spectral lines for each element.

Question 17

True or false:

An electron can skip intermediate energy levels during a transition.

Answer 17

True

The transition depends on the energy absorbed or emitted, not the path.

Question 18

True or false:

Electron transitions can only occur in visible light wavelengths.

Answer 18

False

Transitions can occur across the electromagnetic spectrum, including UV and infrared.

Question 19

What is the significance of the Rydberg formula?

Answer 19

It calculates the wavelengths of light emitted or absorbed during electron transitions in hydrogen atoms.

This formula applies to transitions in hydrogen’s energy levels.

Question 20

What equation relates a photon’s energy (E) to its wavelength (λ)?

Answer 20

E=hc/λ

Where:
λ is the wavelength,
h is the Planck constant, and
c is the speed of light.

Question 21

Fill in the blank:

Electrons closer to the nucleus have _______ energy compared to electrons farther away.

Answer 21

lower

The attraction to the positively charged nucleus reduces the energy of inner electrons.

Question 22

How do energy transitions relate to chemical reactions?

Answer 22

They influence bond formation, bond breaking, and the release or absorption of energy.

Electron transitions are key to understanding reactivity and energy changes.

Question 23

Explain how ionization energy relates to electron transitions.

Answer 23

It’s the amount of energy needed to remove an electron from an atom.

This energy is sufficient to force the electron to transition beyond the atom’s highest energy level and escape its attraction to the nucleus.

Question 24

What are atomic spectra?

Answer 24

The fingerprints of different elements, represented as an array of lines produced by light emitted or absorbed due to their chemical composition.

They are used to determine the composition of various materials, including stars.

Question 25

# Define: Emission spectrum

Answer 25

A series of **bright lines produced when excited electrons release energy** as they transition from higher to lower energy levels. ## Footnote The emission spectrum reflects the energy gap between electron levels—larger gaps produce higher-energy (shorter wavelength) light, while smaller gaps produce lower-energy (longer wavelength) light.

Question 26

What type of spectrum results when **electrons absorb energy**?

Answer 26

Absorption spectrum ## Footnote The absorption spectrum shows dark lines at specific wavelengths where electrons absorb light to jump to higher energy levels. These lines identify the elements present and are the inverse of emission spectra.

Question 27

# Fill in the blank: **Absorption and emission spectra** demonstrate the \_\_\_\_\_\_\_\_ nature of **energy levels** in atoms.

Answer 27

quantized ## Footnote Energy changes occur in fixed amounts, corresponding to specific wavelengths.

Question 28

# Fill in the blank: In a hydrogen atom, transitions involving the first energy level produce the \_\_\_\_\_\_\_ series.

Answer 28

Lyman ## Footnote The Lyman series involves electron transitions to the first energy level (n=1), emitting ultraviolet radiation that is not visible to the human eye but is crucial in astronomical spectroscopy and hydrogen analysis.

Question 29

# Define: Fraunhofer lines

Answer 29

The **missing parts in the Sun's spectrum**, identified as dark lines. ## Footnote They represent specific wavelengths of light absorbed by elements in the solar atmosphere.

Question 30

# True or false: Absorption and emission spectra are **inversely related**.

Answer 30

True ## Footnote The wavelengths absorbed in an absorption spectrum match those emitted in an emission spectrum.

Question 31

What is the main difference between **continuous spectra** and **emission spectra**?

Answer 31

* Continuous spectra show **all wavelengths**. * Emission spectra **display specific** lines. ## Footnote A continuous spectrum displays all wavelengths of visible light without interruption. In contrast, an emission spectrum shows specific bright lines at certain wavelengths, produced when electrons in atoms emit energy as they drop to lower energy levels.

Question 32

In which **industries** is atomic spectroscopy used?

Answer 32

* Metallurgy * Pharmaceuticals * Astronomy * Mechanical engineering * Environmental sciences * Analytical chemistry ## Footnote These industries use spectroscopy to help determine material composition and assess quality and contamination.

Question 33

Explain how absorption spectra are used in **astronomy**.

Answer 33

They identify the **chemical composition** of stars and galaxies. ## Footnote Each element has a unique pattern of absorption lines.

Question 34

# Define: Spectroscopy

Answer 34

The study of **how light interacts with matter** to analyze the composition, structure, and properties of substances. ## Footnote It involves measuring the absorption, emission, or scattering of light across different wavelengths.

Question 35

# Fill in the blank: In **absorption spectroscopy**, the substance absorbs specific wavelengths of light, creating \_\_\_\_\_\_ \_\_\_\_\_\_ in the spectrum.

Answer 35

dark lines ## Footnote These lines correspond to the wavelengths absorbed by the electrons as they transition to higher energy levels.

Question 36

How does spectroscopy help in determining the **age of stars**?

Answer 36

By analyzing the spectral lines in a star's light, astronomers can **estimate its age** based on clues such as chemical composition and temperature. ## Footnote Younger stars typically have higher levels of certain elements like lithium.

Question 37

How is spectroscopy applied in **forensic science**?

Answer 37

It is used to **analyze** blood, hair, fibers, or chemical substances at crime scenes. ## Footnote Infrared (IR) and Raman spectroscopy detect unique chemical signatures by analyzing how substances absorb or scatter light. These techniques help forensic scientists differentiate similar materials, identify unknown substances, and provide reliable evidence in criminal investigations.

Question 38

Explain how spectroscopy is used in **environmental science**.

Answer 38

It is used to **detect, monitor, and quantify pollutants** in air, water, and soil. ## Footnote Spectroscopic methods like UV-Vis spectroscopy can identify harmful chemicals at low concentrations.

Question 39

In medicine, how does spectroscopy assist in **diagnostic imaging**?

Answer 39

MRI and PET scans **analyze body tissues**, aiding in disease detection, such as tumors or brain abnormalities. ## Footnote MRI and PET scans rely on spectroscopic principles by measuring how body tissues absorb and emit specific forms of energy. MRI detects radiofrequency energy changes in hydrogen nuclei, while PET scans track gamma ray emissions from injected tracers, enabling early disease detection and precise organ imaging.

Question 40

# True or false: Spectroscopy is used to study the atomic and molecular **properties of materials**, helping develop new compounds and materials.

Answer 40

True ## Footnote Techniques like X-ray diffraction and infrared spectroscopy are used to reveal the structure and properties of materials, which is essential in creating new materials for various industries.

Question 41

What occurs when white light passes through a **gas sample and then a prism**?

Answer 41

An absorption spectrum is observed, and it displays a **continuous range of colors interrupted by dark lines**. ## Footnote This demonstrates how gas atoms absorb specific wavelengths of light.

Question 42

# Fill in the blank: In a flame test experiment, different **elements emit** distinct \_\_\_\_\_\_\_ when heated.

Answer 42

Colors ## Footnote The colors correspond to emission spectra from electron transitions.

Question 43

# True or false: A **spectroscope** can be used in the classroom to observe both absorption and emission spectra.

Answer 43

True ## Footnote A spectroscope works by dispersing light into its component wavelengths, revealing spectral lines. Dark lines indicate absorbed wavelengths (absorption spectra), while bright lines show emitted wavelengths (emission spectra), providing insights into an element’s composition and electron transitions.

Question 44

# Case Study: If sodium is burned in a flame, it produces a **bright yellow emission line**. What does this reveal about sodium's electron transitions?

Answer 44

Sodium electrons release **energy specific to the yellow wavelength** during transitions. ## Footnote This is part of sodium's unique emission spectrum.

Question 45

What simple experiment can demonstrate **absorption spectra** in the classroom?

Answer 45

Shining **white light through colored filters** or gas tubes and observing with a spectroscope. ## Footnote Filters or gases absorb specific wavelengths, leaving dark lines.

Question 46

Explain how the **spectra of streetlights** (e.g., sodium or mercury vapor) can be analyzed in a classroom.

Answer 46

Using a **handheld spectroscope**, students can identify the emission lines unique to the light source. ## Footnote Each type of lamp has a distinct spectral fingerprint.

Question 47

# Fill in the blank: In a spectroscope experiment, \_\_\_\_\_\_\_ lines indicate the **wavelengths of light** emitted by a gas.

Answer 47

bright ## Footnote These lines correspond to specific electron transitions.

Question 48

How can CDs or DVDs be used in a classroom activity to observe and study **light spectra**?

Answer 48

Students can use a CD as a **diffraction grating** to observe spectra from light sources like lamps or the sun. ## Footnote CDs act as a simple tool to split light into its spectral components.

Question 49

Why are **flame tests** a common classroom experiment for studying emission spectra?

Answer 49

They **visually demonstrate** how different elements emit distinct colors, corresponding to their spectra. ## Footnote This is a simple, hands-on way to explore atomic electron transitions.