Review: Unit 3 Exam - Atomic Structure, Light, and Quantum Mechanics

Comprehensive practice flashcards covering Unit 3: atomic structure, light calculations, electron configurations, quantum numbers, periodic trends, and atomic models.

What is the definition of wavelength ($\lambda$)?

The distance between successive wave peaks.

What is the definition of frequency ($\nu$)?

The number of wave cycles passing a point per second.

What is a photon?

A packet of electromagnetic energy.

What does it mean for electron energy levels in an atom to be quantized?

It means electrons can occupy only specific allowed energy levels.

What occurs when an electron absorbs energy versus when it moves to a lower energy level?

When an electron absorbs energy, it can move to a higher energy level; when an electron moves to a lower energy level, it emits a photon.

What two equations relate light frequency, wavelength, and photon energy, and what are the values of the constants $c$ and $h$?

The equations are $\nu = \frac{c}{\lambda}$ and $E = h\nu$, where the speed of light is $c = 2.998 \times 10^8\,\text{m/s}$ and Planck's constant is $h = 6.626 \times 10^{-34}\,\text{J}\cdot\text{s}$.

How do frequency and wavelength relate to photon energy?

Higher frequency and shorter wavelength correspond to higher photon energy, whereas longer wavelength corresponds to lower photon energy.

Between Photon A with a wavelength of $400\,\text{nm}$ and Photon B with a wavelength of $700\,\text{nm}$, which has higher energy?

Photon A has higher energy because shorter wavelengths correspond to higher photon energy.

Why do elements in the same group on the periodic table display similar chemical properties?

bc they have similar valence-electron configurations

Why does atomic radius generally increase down a group in the periodic table?

____ increases down a group because additional occupied principal energy levels and shielding place the outer electrons farther from the nucleus.

What is electron shielding?

Shielding occurs when inner electrons reduce the electrostatic attraction between the nucleus and outer electrons.

How do metals and nonmetals typically form ions, and what are their respective ion names?

Metals commonly lose electrons to form positive ions called cations, whereas nonmetals commonly gain electrons to form negative ions called anions.

From which energy level are electrons removed first when common main-group cations form?

Electrons are removed from the highest occupied principal energy level first.

Why does ion formation alter an atom's electron configuration without changing its atomic number?

Ion formation involves the gain or loss of electrons, while the number of protons in the nucleus remains unchanged.

What is an emission spectrum, and how can it be used by scientists?

An emission spectrum contains specific wavelengths of light emitted by an atom; each element has a unique, characteristic emission spectrum that serves as evidence to identify the element.

What is the uncertainty principle?

The principle stating that an electron's exact position and momentum cannot both be known with unlimited precision.

How does the quantum-mechanical model describe electrons differently from the Bohr model?

The Bohr model describes electrons traveling along fixed circular paths at quantized energy levels, whereas the quantum-mechanical model describes electrons using orbitals and three-dimensional probability distributions, accounting for subshells and multielectron behavior.

What is one key strength of the Bohr model?

It is especially useful for introducing quantized energy levels and explaining the absorption and emission of particular energies in hydrogen.

What distinguishes paramagnetic substances from diamagnetic substances?

Paramagnetic substances have one or more unpaired electrons and are attracted to a magnetic field, while diamagnetic substances have all electrons paired and are weakly repelled by a magnetic field.

What does Hund's rule state?

Electrons occupy equal-energy orbitals singly, with parallel spins, before pairing.

Why is counting the total number of electrons insufficient to determine whether an atom or ion is paramagnetic or diamagnetic?

Magnetic properties depend on the arrangement of electrons in specific orbitals and whether unpaired electrons exist, meaning two species with the same total electron count can have different pairing configurations.

What distinct roles do an emission spectrum and a periodic-table position play in scientific reasoning?

An emission spectrum provides evidence to identify the element, whereas its position on the periodic table provides information about valence electrons to predict chemical behavior and common ion charges.

For a neutral atom with 19 electrons, what is the element, its abbreviated electron configuration, and its common ion configuration?

The element is potassium ($\text{K}$), its abbreviated configuration is $[\text{Ar}]\,4s^1$, and the configuration of its most common ion ($\text{K}^+$) is $[\text{Ar}]$.

How do core electrons differ from valence electrons in their role in chemical behavior?

Valence electrons reside in the outermost occupied energy level and are most directly involved in bonding and chemical reactions, while core electrons are inner electrons that mainly provide shielding.

What does the principal quantum number ($n$) describe, and what are its allowed values?

It describes the main energy level, and its allowed values are $1, 2, 3, \dots$.

What does the angular momentum quantum number ($l$) describe, and what are its allowed values?

It describes the subshell, and its allowed values are integers from $0$ through $n - 1$.

What does the magnetic quantum number ($m_l$) describe, and what are its allowed values?

It describes orbital orientation, and its allowed values range from $-l$ through $+l$.

What does the spin quantum number ($m_s$) describe, and what are its allowed values?

It describes the electron spin, and its allowed values are $+\frac{1}{2}$ and $-\frac{1}{2}$.

What are the $l$ values, number of orbitals, and maximum electron capacities for $s$, $p$, $d$, and $f$ subshells?

$s$ has $l = 0$, 1 orbital, and max 2 electrons; $p$ has $l = 1$, 3 orbitals, and max 6 electrons; $d$ has $l = 2$, 5 orbitals, and max 10 electrons; $f$ has $l = 3$, 7 orbitals, and max 14 electrons.

For an electron with principal quantum number $n = 3$, what are all possible values of $l$?

The allowed values of $l$ are $0, 1,$ and $2$.

For an electron in a $5p$ subshell, what are all possible values of $m_l$ and $m_s$?

The possible values for $m_l$ are $-1, 0, +1$, and the possible values for $m_s$ are $+\frac{1}{2}$ and $-\frac{1}{2}$.

What is the abbreviated electron configuration of phosphorus ($\text{P}$), and which subshell contains its last electron?

The abbreviated electron configuration is $[\text{Ne}]\,3s^2\,3p^3$, and the subshell containing its last electron is $3p$.