CHEM 1315 Unit 2: The Quantum-Mechanical Model of the Atom and Periodicity

Vocabulary flashcards covering atomic structure, wave-particle duality, Bohr model, quantum numbers, electron configurations, and periodic trends based on CHEM 1315 Unit 2 lecture notes.

Nucleus

A very tiny volume that comprises most of the mass of an atom and contains positive protons and neutral neutrons.

Electrons

Subatomic particles that occupy most of an atom's volume, have very low mass, are negatively charged, and are in constant motion.

Protons

Positively charged subatomic particles that determine the identity of an element.

Neutrons

Neutral subatomic particles that vary in number within an element to yield isotopes.

Electromagnetic radiation

A form of energy that has wave characteristics and propagates through a vacuum at the characteristic speed of $3.00 \times 10^8\,m/s$.

Frequency ($\nu$)

The number of wave cycles per unit time, mathematically defined by $\nu\lambda = c$, where $1\,Hz = 1\,s^{-1}$.

Wavelength ($\lambda$)

The distance between corresponding points on adjacent waves, inversely related to frequency by $\nu\lambda = c$.

Quantum

The smallest increment of radiant energy that may be absorbed or emitted, defined by $E_{\text{quanta}} = h\nu$.

Planck's constant ($h$)

A fundamental physical constant with a value of $6.62607015 \times 10^{-34}\,J \cdot s$ used to relate wave frequency to energy.

Photon

A discrete packet or quantum of light energy, where $E_{\text{photon}} = h\nu$.

Diffraction

The bending of traveling waves around an obstacle or opening in a barrier that is about the same size as the wavelength.

Constructive interference

The interaction of waves that are in phase, combining to produce a wave of larger amplitude.

Destructive interference

The interaction of waves that are out of phase, canceling each other out.

Photoelectric Effect

The emission or ejection of electrons from a metal surface when light shines upon it.

Threshold Frequency

The minimum frequency of light below which no electrons are ejected from a metal surface, regardless of the light's intensity.

Binding energy ($\phi$)

The energy required for an electron to escape from a metal surface, where any excess absorbed photon energy becomes kinetic energy: $\text{KE} = h\nu - \phi$.

Classical Mechanics

A deterministic model of the macroscopic world where exact positions and velocities calculate precise trajectories.

Quantum Mechanics

A probabilistic model of the sub-microscopic world that incorporates both wave and particle properties of matter.

Atomic Spectroscopy

The study of electromagnetic radiation absorbed and emitted by atoms.

Emission spectrum

The pattern of spectral lines formed when light emitted from excited gas atoms passes through a slit and a prism.

Principal Quantum Number ($n$)

An integer quantum number ($n \ge 1$) that describes the main energy level or shell in which an orbital resides.

Angular momentum quantum number ($\ell$)

A quantum number with integer values ranging from $0$ to $n - 1$ that defines the shape of an atomic orbital.

Magnetic Quantum Number ($m_\ell$)

An integer quantum number ranging from $-\ell$ to $\ell$ ($-\ell \le m_\ell \le \ell$) that specifies the spatial orientation of an orbital.

Spin Quantum Number ($m_s$)

A quantum number taking values of $+\frac{1}{2}$ or $-\frac{1}{2}$ that describes the orientation of an electron's spin.

Aufbau principle

The rule stating that electrons fill the lowest available orbital energy levels before occupying higher energy levels.

Pauli Exclusion Principle

The principle stating that no two electrons in an atom can have identical sets of four quantum numbers, limiting each orbital to two electrons with opposite spins.

Hund's Rule

The rule stating that for degenerate orbitals, the lowest energy is attained when the number of electrons with the same spin is maximized.

Degenerate orbitals

Atomic orbitals that possess the exact same energy level.

Isoelectronic series

A group of atoms or ions that share the exact same number of electrons.

Effective Nuclear Charge ($Z_{\text{eff}}$)

The net positive charge and total attraction felt by an electron toward the nucleus, calculated as $Z_{\text{eff}} = Z - S$.

Ionization energy

The amount of energy required to remove an electron from the ground state of a gaseous atom or ion.

Electron Affinity

The energy change associated with adding an electron to a gaseous atom.