Properties of Light, Spectroscopy, and Orbital Theory

Flashcards covering the properties of light, spectroscopy, wave vocabulary, ionization energy, atomic orbitals, hybridization, and molecular orbital theory as presented in Lectures 32 through 40.

Wavelength

Represented by the symbol $\lambda$ (lambda), it is the distance between two peaks of a wave and is typically measured in meters ($m$).

Frequency

Represented by the symbol $\nu$ (nu), it is the number of peaks that cross a finish line per second, measured in $s^{-1}$ or $Hz$.

Speed of light (c)

A constant value representing how fast light travels, calculated as $c = \lambda \times \nu$, and is equal to $3 \times 10^{8}\,m/s$.

Amplitude (A)

The distance from a wave's midline to either the top of a peak or the bottom of a valley, which determines light intensity or brightness.

Rotational excitation

A change in matter caused by absorbing light that results in molecules in a sample starting to rotate faster.

Vibrational excitation

A change in matter resulting from light absorption that causes the stretching and contracting of molecular bonds.

Photon

A particle of light whose energy depends on its frequency, represented by the equation $E = h\nu$.

Planck's constant (h)

A physical constant used in the calculation of photon energy, with a value of $6.626 \times 10^{-34}\,J\,s$.

The Photoelectric Effect

The phenomenon where photons with sufficient energy eject electrons from metal; energy beyond the threshold is converted to the electron's kinetic energy ($E(\text{light}) - E(\text{threshold}) = KE(\text{electron})$).

Binding energy

The Coulombic attraction between electrons and the nucleus, calculated as $E(\text{light}) - KE(\text{electron})$ and also known as ionization energy.

Ionization Energy (IE)

The energy required for the process $X(g) \rightarrow X^{+}(g) + e^{-}$, which increases across a row as $Z_{\text{eff}}$ increases.

Electron Affinity (EA)

The energy released when an electron is added to an atom, which generally gets more negative across a row as $Z_{\text{eff}}$ increases.

Shell Model Energy Equation

An equation used for single-electron examples like $H$, $He^{+}$, or $Li^{2+}$, defined as $E(n) = -Ry\left(\frac{z^2}{n^2}\right)$, where $Ry = 1312\,kJ/mol$.

Constructive Interference

A process where a reflected wave pulse matches up with an incoming wave pulse to amplify the wave, creating a "standing wave."

Orbital

A map of a 3D standing wave enclosing the area where an electron is $90\%$ likely to be found.

Angular node

A flat node within a three-dimensional standing wave or orbital.

Radial node

A spherical node within a three-dimensional standing wave or orbital.

Sigma (σ) bond

A type of covalent bond where orbital overlap occurs directly in between the two nuclei.

Pi (π) bond

A type of covalent bond formed by the overlap of p orbitals above and below the nuclei; a pair of atoms can have up to two of these bonds.

Hybrid Orbitals

Equivalent orbitals (like $sp$, $sp^2$, or $sp^3$) formed from mixing s and p orbitals to account for observed molecular geometries.

Molecular Orbitals (MO)

New orbitals formed when atomic orbitals combine; they belong to the entire molecule rather than any particular atom.

HOMO

The Highest Occupied Molecular Orbital in a molecular orbital diagram.

LUMO

The Lowest Unoccupied Molecular Orbital in a molecular orbital diagram.

Bond Order

A calculation involving bonding and antibonding orbitals used to predict the stability and number of bonds between atoms.