AP Chem: Quantum Mechanics(Chapter 7)

• Q: What is the fundamental difference between quantum mechanics and Newton-classical mechanics according to the notes?

• A: Quantum mechanics is the "driving force to understanding properties of atoms/molecules that are not governed by the same laws as larger molecules (macroscopic)"

• Q: Define wavelength (λ) and frequency (ν) in the context of a wave, and state the unit for frequency.

• A: Wavelength (λ) is the "distance between identical points on a continuous wave". Frequency (ν) is the "number of waves that pass a given point per second". The unit for frequency is Hz (1/s).

• Q: What is the speed of light (c) and what is its relationship to wavelength and frequency?

• A: The speed of light (c) is 2.998 x 10⁸ m/s. It is related to wavelength (λ) and frequency (ν) by the formula: c = λν. There is an inverse relationship between wavelength and frequency.

• Q: What are the two components of electromagnetic waves?

• A: Electromagnetic waves consist of an electric field component and a magnetic field component

• Q: According to Planck, what does it mean that energy is "quantized"? What are the "bundles of energy" called?

vA: Planck stated that energy is "quantized," meaning atoms/molecules can only emit/absorb energy in discrete quantities. These "bundles of energy" are called photons, and each contains "1 quantum of energy

• Q: Explain Einstein's photoelectric effect.

A: The photoelectric effect is when "electrons are ejected from a metal surface if exposed to light of a minimum frequency". This demonstrates the wave-particle duality of light.

• Q: What were the two key ideas of the 1913 Bohr Model regarding electron behavior?

• A: The Bohr Model proposed a planetary orbit model where "electrons orbit the nucleus at fixed distances". It also introduced the concept of energy levels (n=1, 2, 3...), which are not equidistant.

• Q: For which atom did the Bohr Model work successfully?

• A: The Bohr Model only worked for Hydrogen

• Q: How did the Bohr Model explain the "emission spectrum" of gaseous elements?

• A: The Bohr Model's concept of electrons existing in specific energy levels explained why "different elements emit different colors," leading to the idea of "emission spectrums (fingerprints)" for gaseous elements

• Q: How did DeBroglie extend Bohr's model?

• A: DeBroglie took Bohr's model "one step further" by proposing the dual nature of energy, stating that "energy is both particle and wavelike". He suggested that "anything that has a mass also have a wavelength".

• Q: What does the Heisenberg uncertainty principle state?

• A: The Heisenberg uncertainty principle states that "it is impossible to know both the position (x) and momentum (p) of an electron with certainty"

• Q: How did Schrödinger describe the location of electrons, and what concept did he develop?

A: Schrödinger "developed wave equations to determine the probability of where electrons are". He introduced the concept of an electron cloud and developed orbitals, which are 3D regions of space where electrons are likely to be found

• Q: What are the four types of sublevels and at which energy level (n) do they start?

A:

    ◦ s sublevel starts at energy level 1.

    ◦ p sublevel starts at energy level 2.

    ◦ d sublevel starts at energy level 3.

    ◦ f sublevel starts at energy level 4.

• Q: State the Pauli exclusion principle.

A: The Pauli exclusion principle states: "If two electrons are in the same energy level and same orbital, they must have opposite spins".

Q: What is Aufbau's principle?

• A: Aufbau's principle states that "sublevels should be filled from lowest energy to highest energy"

• Q: Explain Hund's rule.

: Hund's rule states that "the lowest energy arrangement of electrons within a sublevel is the one with the most parallel spins". This helps to "minimize e⁻-e⁻ repulsion".

Q: What is the definition of an excited state for an electron?

A: An excited state is "when an electron is at a higher energy than in ground state".

Q: What are valence electrons? What is the maximum number of valence electrons an atom can have?

A: Valence electrons are "electrons in the outermost ENERGY LEVEL". The maximum number of valence electrons an atom can have is 8.

• Q: Distinguish between diamagnetic and paramagnetic atoms.

A: Atoms with no unpaired electrons are diamagnetic and have "no magnetic charge". Atoms with unpaired electrons are paramagnetic and are "attracted to a magnetic field".