Ch.7 - Quantum MechanicsSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Electrons can move up and down to different orbitals or shells based on absorbing or releasing of energy. 

Bohr's Model of the Atom

Concept #1: Understanding the Atom

Bohr's Model tries to explain what happens to the electron when it absorbs or emits energy. 

Concept #2: Absorption vs. Emission

In absorption, an electron gains energy and becomes excited. In this excited state, the electron moves to higher energy level. 

In emission, the electron releases its excess energy to go down to a lower energy level.

Example #1: Calculate the energy of the 4th electron found in the n = 2 state of the boron atom in kilojoules per mole. 

Practice: Which of the following transitions (in a hydrogen atom) represents emission of the longest wavelength?

Practice: Which of the following transitions represents absorption of a photon with the largest energy?    

Atomic Emission

Concept #3: Understanding Absorption & Emission

Concept #4: Different Emission Series

We know that emission is the releasing of energy, but different energies are released depending on which shell the electron falls. These different energies appear in different places on the electromagnetic spectrum. 

Example #2: What is the wavelength of a photon (in nanometers) emitted during a transition from n = 4 to n = 2 state in the hydrogen atom?

Practice: Classify each of the following transitions as either a Lyman, Balmer or Paschen series. a) n = 3 to n = 1 b) n = 6 to n = 1 c) n = 3 to n = 2 d) n = 6 to n = 3 e) n = 4 to n = 2

Additional Problems
Which transition between energy levels in a hydrogen atom corresponds to the shortest wavelength of light? 1. 5 → 6 2. 2 → 5 3. 2 → 3 4. 3 → 5 5. 3 → 4 6. 2 → 4 
Which energy gap in the Bohr Model would be associated with the longest wavelength?(A) from n = 2 to n = 1(B) from n = 6 to n = 5(C) from n= 10 to n = 9(D) from n = 11 to n = 10(E) They have the same wavelength
Is energy emitted or absorbed when the following electronic transitions occur in hydrogen: (a) from n = 4 to n = 2
Which electronic transition in atomic hydrogen corresponds to the emission of visible light?a) n = 5 → n = 2b) n = 1 → n = 2c) n = 3 → n = 4d) n = 3 → n = 1 
Indicate whether energy is emitted or absorbed when the following electronic transitions occur in hydrogen: (a) from n = 2 to n = 6
Consider the process of 2 H(g) → H2(g) where ΔH = −436 kJ/molDetermine if the sentence below is true or false.Shining light on hydrogen atoms could put electrons in  n = 3, provided the intensity was sufficiently high.
Which of the following concepts/models/phenomena are related to “quantized energy levels”? a. Fireworksb. Neils Bohr’s model for the atomc. The “line spectra” of helium emissiond. Both (a) and (b)e. All if the above
How many unique emission lines are observed from a system with four equally spaced energy levels?a. 1b. 2c. 3d. 4e. 5
Which electronic transition in the hydrogen atom results in the emission of light of the shortest wavelength?A. n = 4 to n = 3B. n = 1 to n = 2C. n = 1 to n = 6D. n = 3 to n = 1E. n = 2 to n = 1
The lines in an atomic absorption spectrum are due to1. the presence of isotopes.2. movement of electrons from higher energy states to lower energy states in atoms.3. nuclear transitions in atoms.4. movement of electrons from lower energy states to higher energy states in atoms. 
Using the figure down below, complete the following statement: When an electron undergoes Transition A, it ________ energy, and when it undergoes Transition B, it ________ energy and __________. A. absorbs, emits, absorbs electromagnetic radiationB. absorbs, releases, absorbs electromagnetic radiationC. absorbs, releases, emits electromagnetic radiationD. releases, absorbs, absorbs electromagnetic radiationE. releases, absorbs, emits electromagnetic radiation
One of the emission lines of the hydrogen atom has a wavelength of 93.8 nm. (a) In what region of the electromagnetic spectrum is this emission found?
Which of the following statements is/are true?a. An emission spectrum is formed when a beam of white light passes through a sample of gasb. An emission spectrum is formed by an electric current passing through a gas in a vacuum tubec. The photoelectric effect is due to particle-like behavior of lightd. The photoelectric effect is due to wave behavior of light1. A & C2. B & D3. A & D4. B & C5. C & D
For a hydrogen atom, which case will result in an absorption spectrum with the highest frequency?a.  an electron transition from n = 1 → n = 2b.  an electron transitions from n = 1 → n = 4c.  an electron transition from n = 2 → n = 3d.  an electron transitions from n = 3 → n = 1e.  an electron transition from n = 4 → n = 3
Which of the following electron transitions requires the smallest energy to be absorbed by the hydrogen atom?A. from n = 1 to n = 2B. from n = 2 to n = 4C. from n = 2 to n = 6D. from n = 3 to n = 6E. from n = 4 to n = 6
Complete this sentence: Atoms emit visible and ultraviolet light a. as electrons jump from lower energy levels to higher levels. b. as the atoms condense from a gas to a liquid. c. as electrons jump from higher energy levels to lower levels. d. as they are heated and the solid melts to form a liquid. e. as the electrons move about the atom within an orbit.
The lines in the emission spectrum of hydrogen result from __________. A) electrons given off by hydrogen as it coolsB) decomposing hydrogen atomsC) electrons given off by hydrogen when it burnsD) energy given off in the form of visible light when an electron moves from a higher energy state to a lower energy stateE) protons given off when hydrogen burns
The lines in the emission spectrum of hydrogen result from ___________________ .A) electrons given off by hydrogen as it coolsB) decomposing hydrogen atomsC) electrons given off by hydrogen when it burnsD) energy given off in the form of visible light when an electron moves from a higher energy state to a lower energy stateE) protons given off when hydrogen burns
The lines in an atomic absorption spectrum are due to1. the presence of isotopes.2. movement of electrons from higher energy states to lower energy states in atoms.3. nuclear transitions in atoms4. movement of electrons from lower energy states to higher energy states in atoms.
According to the Bohr model for the hydrogen atom, which of the following transitions will emit light with the longest wavelength? a. from the n = 4 to n = 2 energy level. b. from the n = 4 to n = 3 energy level. c. from the n = 3 to n = 1 energy level. d. from the n = 6 to n = 2 energy level. e. from the n = 5 to n = 3 energy level.
Which match is incorrect?a) de Broglie       Predicted that matter had a wave natureb) Planck            Proposed that energy is released/absorbed in quantized packets of a photon c) Bohr               Electron in hydrogen can only occupy orbits with energies of fixed valued) Heisenberg    Proposed that electrons orbit the nucleus in well-defined spherical orbitse) Einstein         Radiant energy is quantized in packets called photons
The existence of discrete (quantized) energy levels in an atom may be inferred from (A) experiments on the photoelectric effect.(B) diffraction of electrons by crystals.(C) X-ray diffraction by crystals(D) atomic line spectra
Which emission line in the hydrogen spectrum occurs at the highest frequency?a) n = 3 → n = 1b) n = 4 → n = 2c) n = 7 → n = 5d) n = 10 → n = 8
Which of the following transitions (in a hydrogen atom) represent  emission of the smallest or shortest wavelength? n = 4 to n = 2n = 3 to n=  4n = 1 to n = 2n = 7 to n = 5n = 2 to n = 5
Which of the following experiments in quantum mechanics is NOT correctly summarized?a. Photoelectric Effect: High intensity, high energy light cannot eject electrons from a metal plate. This means energy cannot be transferred from light to electrons.b. Heisenberg’s Uncertainty Principle: The more precisely you know the position of an electron, the less precisely you can know its velocityc. Atomic emission spectra: When Argon gas is heated, the gas emits light with discrete energy levels, rather than a continuous spectrum. This indicates that electrons are not found at random energy levels in an atom, but at energy levels that are quantized.d. Electron Diffraction: When firing electrons one at a time toward at a grating, an interference pattern is generated. This indicates that electrons behave like waves.
Which of the following transitions represent  absorption of a photon with the  highest frequency? n = 3 to n = 1n = 2 to n = 4n = 1 to n = 2n = 6 to n = 3n = 1 to n = 3 
Which of the following emission lines corresponds to part of the Balmer series of lines in the spectrum of a hydrogen atom?A) n2 → n1B) n4 → n2C) n4 → n1D) n3 → n2E) n4 → n3 1. B and D only2. E only3. A and C only4. A, D, and E only5. B and C only 
Which of the following transitions represent the  emission  of a photon with the largest energy?A) n = 1 to n = 4B) n = 2 to n = 5C) n = 3 to n = 1D) n = 6 to n = 3E) n = 2 to n = 1
Which of the following statements is or are true?1. An excited atom can return to a lower energy level by absorbing light energy.2. An atom can be excited by emitting light energy.3. As the energy of electromagnetic radiation increases, its frequency increases.4. The frequency and wavelength of light are inversely proportional.a) 1 and 2 onlyb) 2 onlyc) 2 and 3d) 1 and 3e) 3 and 4
According to the Bohr model for the hydrogen atom, the energy necessary to excite an electron from n = 1 to n = 2 is _______ the energy necessary to excite an electron from n = 5 to n = 6. equal to either less or equal to greater than less than either equal to or greater than
According to the quantum-mechanical model for the hydrogen atom, which electron transition would produce light with the longest wavelength?4p → 3p 4s → 3p 5s → 4p 3p → 2a 2p → 1s
Which electron transition produces light of the highest frequency in the hydrogen atom?a. 2p → 1sb. 4p → 1sc. 3p → 1sd. 5p → 1s
According to the Bohr atomic theory, when an electron moves from one energy level to another further from the nucleusa) energy has been absorbedb) energy has been emittedc) light has been emittedd) photons have been dischargede) no change in energy is observed
Atoms emit visible, IR, and UV light _____________ a) as electrons jump from lower energy levels to higher levels.b) as electrons drop from higher energy levels to lower levels.c) As they are heated and the solid melts to form a liquid.d) As the atoms condense from a gas to a liquid.e) As the electrons move about the atom within an orbit.  The order of the lower energy levels for the question above area) 1, 2, 3b) 3, 2, 1c) 2, 3, 1d) 2, 1, 3e) 1, 3, 2
An electron in the n=7 level of the hydrogen atom relaxes to a lower energy level, emitting light of 2166 nm. What is the value of n for the level to which the electron relaxed?
The energies, E, for the first few states of an unknown element are shown here in arbitrary units.
Calculate the wavelength, in nanometers, of the spectral line produced when an electron in a hydrogen atom undergoes the transition from the energy level n = 7 to the level n = 2.
What are the wavelengths, in nanometers, of the bright lines of the hydrogen emission spectrum corresponding to the transition: n = 5 to n = 2.
Atomic emission spectra are due to electronsa. being removed from an atom.b. in an atom rising from one energy level to a higher one.c. in an atom dropping from one energy level to a lower one.d. being added to an atom. changing state from solid to liquid.