MCAT Chemical and Physical Foundations of Biological Systems Flashcards: 4e Electronic Structure Quantum Models

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This deck focuses on 4e Electronic Structure Quantum Models, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Chemical and Physical Foundations of Biological Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What does Hund's rule state about filling degenerate orbitals?

Answer: Maximize unpaired electrons before pairing. Hund's rule minimizes electron-electron repulsion by maximizing spin multiplicity in degenerate orbitals.

Flashcard 2: What does the Pauli exclusion principle state for electrons in an atom?

Answer: No two electrons share the same 4 quantum numbers. Pauli exclusion ensures electrons are fermions, requiring unique sets of quantum numbers for indistinguishability and antisymmetry.

Flashcard 3: What is the maximum number of electrons in the $n$th principal shell?

Answer: $2n^2$ electrons. The $n$th shell's capacity derives from summing subshell maxima, yielding $2n^2$ electrons total.

Flashcard 4: What is the maximum number of electrons in a subshell with quantum number $\ell$?

Answer: $2(2\ell + 1)$ electrons. Maximum electrons in a subshell equal twice the number of orbitals, accommodating two per orbital with opposite spins.

Flashcard 5: What does the square of the wavefunction magnitude represent in quantum mechanics?

Answer: $|\psi|^2$ is probability density. In the Copenhagen interpretation, the square of the wavefunction's magnitude gives the probability density of finding a particle at a point.

Flashcard 6: What is the relationship between wavelength and frequency for electromagnetic radiation?

Answer: $c = \lambda\nu$. For electromagnetic waves, the speed of light equals the product of wavelength and frequency in vacuum.

Flashcard 7: What is the relationship between photon energy, frequency, and Planck's constant?

Answer: $E = h\nu$. Photon energy is quantized and directly proportional to its frequency, with Planck's constant as the proportionality factor.

Flashcard 8: Which subshell has lower energy in a multielectron atom: $4s$ or $3d$?

Answer: $4s$ is lower energy than $3d$ (fills first). In multielectron atoms, orbital energies depend on $n+\ell$, making $4s$ ($n+\ell=4$) lower than $3d$ ($n+\ell=5$).

Flashcard 9: What is the maximum number of electrons in the $n = 3$ shell?

Answer: $2(3^2) = 18$ electrons. The formula $2n^2$ sums capacities of subshells from $\ell=0$ to $n-1$ for the third shell.

Flashcard 10: State the photon energy equation written in terms of wavelength.

Answer: $E = \frac{hc}{\lambda}$. Photon energy is inversely proportional to wavelength, derived by combining Planck's relation with the speed of light equation.

Flashcard 11: Identify the number of orbitals in the $d$ subshell and its maximum electrons.

Answer: 5 orbitals; 10 electrons. For $d$ subshell ($\ell=2$), $2\ell+1=5$ orbitals accommodate up to 10 electrons following Pauli exclusion.

Flashcard 12: Identify the number of orbitals in the $p$ subshell and its maximum electrons.

Answer: 3 orbitals; 6 electrons. For $p$ subshell ($\ell=1$), $2\ell+1=3$ orbitals hold up to 6 electrons with paired spins.

Flashcard 13: What does the Aufbau principle state about electron filling?

Answer: Electrons fill lowest-energy orbitals first. Aufbau principle follows increasing orbital energies to achieve the ground state electron configuration.

Flashcard 14: What is the maximum number of electrons that can occupy one orbital?

Answer: 2 electrons (opposite spins). Pauli exclusion allows at most two electrons per orbital, requiring opposite spins to differ in $m_s$.

Flashcard 15: How many orbitals exist in a subshell with azimuthal quantum number $\ell$?

Answer: $2\ell + 1$ orbitals. The number of orbitals in a subshell equals the possible $m_\ell$ values, given by $2\ell + 1$.

Flashcard 16: What subshell letters correspond to $\ell = 0,1,2,3$?

Answer: $\ell=0\to s$, $1\to p$, $2\to d$, $3\to f$. Subshell notation uses letters where $s$ ($\ell=0$) is spherical, $p$ ($\ell=1$) dumbbell-shaped, $d$ ($\ell=2$) clover-like, and $f$ ($\ell=3$) more complex.

Flashcard 17: What are the allowed values of $m_\ell$ for a given azimuthal quantum number $\ell$?

Answer: $m_\ell = -\ell,\dots,0,\dots,+\ell$. Allowed $m_\ell$ values are integers from $-\ell$ to $+\ell$, corresponding to possible orientations of orbital angular momentum.

Flashcard 18: What are the allowed values of $\ell$ for a given principal quantum number $n$?

Answer: $\ell = 0,1,\dots,n-1$. Allowed $\ell$ values range from 0 to $n-1$ to ensure subshells fit within the principal shell's energy hierarchy.

Flashcard 19: Which quantum number specifies electron spin, and what values can it take?

Answer: Spin quantum number $m_s = \pm \frac{1}{2}$. Electron spin is an intrinsic property, with $m_s$ taking values of $+\frac{1}{2}$ or $-\frac{1}{2}$ to denote up or down spin.

Flashcard 20: Which quantum number $n$, $\ell$, $m_\ell$, or $m_s$ determines an orbital's orientation in space?

Answer: Magnetic quantum number $m_\ell$. The magnetic quantum number $m_\ell$ specifies the orbital's projection along a magnetic field, defining its spatial orientation.

Flashcard 21: Which quantum number $n$, $\ell$, $m_\ell$, or $m_s$ determines an orbital's shape (subshell)?

Answer: Azimuthal quantum number $\ell$. The azimuthal quantum number $\ell$ specifies the orbital angular momentum, determining the subshell type and shape.

Flashcard 22: Which quantum number $n$, $\ell$, $m_\ell$, or $m_s$ determines an orbital's energy level (shell)?

Answer: Principal quantum number $n$. The principal quantum number $n$ defines the electron's energy level and average distance from the nucleus in hydrogen-like atoms.

Flashcard 23: What is the value relationship between $h$ and $\hbar$?

Answer: $\hbar = \frac{h}{2\pi}$. Reduced Planck's constant is defined as Planck's constant divided by $2\pi$, commonly used in quantum mechanical equations.

Flashcard 24: What is the Heisenberg uncertainty principle relating position and momentum?

Answer: $\Delta x\,\Delta p \geq \frac{\hbar}{2}$. The principle quantifies the limit on simultaneously knowing a particle's position and momentum precisely, reflecting wave-particle duality.

Flashcard 25: What is the de Broglie wavelength of a particle with momentum $p$?

Answer: $\lambda = \frac{h}{p}$. De Broglie's hypothesis states that particles exhibit wave-like properties, with wavelength inversely proportional to momentum via Planck's constant.