2A2 Atomic Spectra and Electron Energy Flashcards
Describe the relationship between atomic spectra, electron energy levels, and electron energy transitions.
Define:
Ground state
The lowest energy configuration of its electrons.
Atoms are most stable in the ground state.
Define:
Electron energy level
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).
What is the principal quantum number?
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.
Who proposed the Bohr model of the atom?
Niels Bohr
in 1913
The Bohr model introduced the concept of quantized energy levels, explaining why electrons occupy specific orbits instead of moving freely.
Fill in the blank:
When an electron moves to a higher energy level, it is in an _______ state.
excited
An electron absorbs energy to move to an excited state, temporarily occupying a higher energy level before returning to its ground state.
What distinguishes the valence shell in an atom?
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.
True or false:
Electrons can transition to any energy level without restriction.
False
Electrons can only transition between quantized energy levels by absorbing or emitting specific amounts of energy, as described by quantum mechanics.
What happens when an electron returns to its ground state?
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.
What factor determines the wavelength of light emitted when an electron transitions between energy levels?
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.
Explain why electrons do not stay in excited states for long.
They lose energy quickly and return to lower energy levels.
This process stabilizes the atom.
Why are emission spectra also called bright-line spectra?
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.
How do electron transitions produce the bright-line spectra of elements?
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.
True or false:
Electrons can move between energy levels without absorbing or emitting energy.
False
Energy must be absorbed or released for a transition to occur.
What happens when an electron absorbs a photon?
It can be excited to a higher energy level.
The photon must have the right energy for this to occur.
Fill in the blank:
When an electron transitions from a higher to a lower energy level, it releases a _______.
photon
The energy of the emitted photon exactly equals the energy difference between the two levels, following the equation E = hƒ (Planck’s equation)
What type of energy is typically involved in electron transitions?
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.
True or false:
An electron can skip intermediate energy levels during a transition.
True
The transition depends on the energy absorbed or emitted, not the path.
True or false:
Electron transitions can only occur in visible light wavelengths.
False
Transitions can occur across the electromagnetic spectrum, including UV and infrared.
What is the significance of the Rydberg formula?
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.
What equation relates a photon’s energy (E) to its wavelength (λ)?
E=hc/λ
Where:
λ is the wavelength,
h is the Planck constant, and
c is the speed of light.
Fill in the blank:
Electrons closer to the nucleus have _______ energy compared to electrons farther away.
lower
The attraction to the positively charged nucleus reduces the energy of inner electrons.
How do energy transitions relate to chemical reactions?
They influence bond formation, bond breaking, and the release or absorption of energy.
Electron transitions are key to understanding reactivity and energy changes.
Explain how ionization energy relates to electron transitions.
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.
What are atomic spectra?
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.
Define:
Emission spectrum
A series of bright lines produced when excited electrons release energy as they transition from higher to lower energy levels.
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.
What type of spectrum results when electrons absorb energy?
Absorption spectrum
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.
Fill in the blank:
Absorption and emission spectra demonstrate the ________ nature of energy levels in atoms.
quantized
Energy changes occur in fixed amounts, corresponding to specific wavelengths.
Fill in the blank:
In a hydrogen atom, transitions involving the first energy level produce the _______ series.
Lyman
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.
Define:
Fraunhofer lines
The missing parts in the Sun’s spectrum, identified as dark lines.
They represent specific wavelengths of light absorbed by elements in the solar atmosphere.
True or false:
Absorption and emission spectra are inversely related.
True
The wavelengths absorbed in an absorption spectrum match those emitted in an emission spectrum.
What is the main difference between continuous spectra and emission spectra?
- Continuous spectra show all wavelengths.
- Emission spectra display specific lines.
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.
In which industries is atomic spectroscopy used?
- Metallurgy
- Pharmaceuticals
- Astronomy
- Mechanical engineering
- Environmental sciences
- Analytical chemistry
These industries use spectroscopy to help determine material composition and assess quality and contamination.
Explain how absorption spectra are used in astronomy.
They identify the chemical composition of stars and galaxies.
Each element has a unique pattern of absorption lines.
Define:
Spectroscopy
The study of how light interacts with matter to analyze the composition, structure, and properties of substances.
It involves measuring the absorption, emission, or scattering of light across different wavelengths.
Fill in the blank:
In absorption spectroscopy, the substance absorbs specific wavelengths of light, creating ______ ______ in the spectrum.
dark lines
These lines correspond to the wavelengths absorbed by the electrons as they transition to higher energy levels.
How does spectroscopy help in determining the age of stars?
By analyzing the spectral lines in a star’s light, astronomers can estimate its age based on clues such as chemical composition and temperature.
Younger stars typically have higher levels of certain elements like lithium.
How is spectroscopy applied in forensic science?
It is used to analyze blood, hair, fibers, or chemical substances at crime scenes.
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.
Explain how spectroscopy is used in environmental science.
It is used to detect, monitor, and quantify pollutants in air, water, and soil.
Spectroscopic methods like UV-Vis spectroscopy can identify harmful chemicals at low concentrations.
In medicine, how does spectroscopy assist in diagnostic imaging?
MRI and PET scans analyze body tissues, aiding in disease detection, such as tumors or brain abnormalities.
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.
True or false:
Spectroscopy is used to study the atomic and molecular properties of materials, helping develop new compounds and materials.
True
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.
What occurs when white light passes through a gas sample and then a prism?
An absorption spectrum is observed, and it displays a continuous range of colors interrupted by dark lines.
This demonstrates how gas atoms absorb specific wavelengths of light.
Fill in the blank:
In a flame test experiment, different elements emit distinct _______ when heated.
Colors
The colors correspond to emission spectra from electron transitions.
True or false:
A spectroscope can be used in the classroom to observe both absorption and emission spectra.
True
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.
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?
Sodium electrons release energy specific to the yellow wavelength during transitions.
This is part of sodium’s unique emission spectrum.
What simple experiment can demonstrate absorption spectra in the classroom?
Shining white light through colored filters or gas tubes and observing with a spectroscope.
Filters or gases absorb specific wavelengths, leaving dark lines.
Explain how the spectra of streetlights (e.g., sodium or mercury vapor) can be analyzed in a classroom.
Using a handheld spectroscope, students can identify the emission lines unique to the light source.
Each type of lamp has a distinct spectral fingerprint.
Fill in the blank:
In a spectroscope experiment, _______ lines indicate the wavelengths of light emitted by a gas.
bright
These lines correspond to specific electron transitions.
How can CDs or DVDs be used in a classroom activity to observe and study light spectra?
Students can use a CD as a diffraction grating to observe spectra from light sources like lamps or the sun.
CDs act as a simple tool to split light into its spectral components.
Why are flame tests a common classroom experiment for studying emission spectra?
They visually demonstrate how different elements emit distinct colors, corresponding to their spectra.
This is a simple, hands-on way to explore atomic electron transitions.
