CEM 141 - Chapter 2: Electrons and Orbitals Flashcards

This set of vocabulary flashcards covers key concepts from Chapter 2 of CEM 141, including wave-particle duality, atomic spectroscopy, quantum mechanical models, electron configurations, and periodic trends.

Electromagnetic Radiation

Energy that can be described as either a particle or a wave, characterized by frequency, wavelength, and speed.

Wavelength ($\lambda$)

The distance in meters ($m$) between successive peaks or troughs of a wave.

Frequency ($\nu$)

The number of wave cycles that pass a point per unit of time, measured in Hertz ($Hz$) or $s^{-1}$.

Amplitude

The height of the peaks of a wave, which is related to the intensity of the light but not its energy.

Speed of Light ($c$)

A constant value representing the speed at which electromagnetic radiation travels, equal to $3.00 \times 10^8\,m\,s^{-1}$.

Diffraction

A property of waves where they bend as they pass through a slit or around a barrier, which particles do not do.

Constructive Interference

An interaction where waves are in-phase, causing crests and troughs to reinforce each other and increase amplitude.

Destructive Interference

An interaction where waves are out-of-phase, causing crests and troughs to cancel each other out.

Photoelectric Effect

The phenomenon where many metals emit electrons when electromagnetic radiation shines on their surface, provided the radiation is above a specific threshold frequency.

Photons

Packets of energy, also known as particles or quanta of light, as postulated by Einstein.

Planck’s Constant ($h$)

A proportionality constant used to calculate the energy of a photon ($E = h\nu$), equal to $6.626 \times 10^{-34}\,J\,s$.

Atomic Emission Spectrum

A spectrum consisting of only specific wavelengths of light emitted by atoms of a particular element.

Atomic Absorption Spectrum

A spectrum showing specific wavelengths of light absorbed by atoms, appearing as dark lines against a continuous background.

Rutherford’s Model

An early atomic model with electrons circling the nucleus like planets, which failed to explain why atoms do not implode or how they emit/absorb spectra.

Bohr Model

A model where electrons move in defined orbits around the nucleus with definite energies, explaining spectra through discrete energy levels.

Heisenberg Uncertainty Principle

The principle stating that we cannot measure accurately both the energy and position of a small particle like an electron simultaneously.

Wave Function ($\Psi$)

A mathematical description of the energies and probabilities of electrons as derived from quantum mechanics.

Atomic Orbitals

Regions of space where electrons with a certain quantized energy have a high probability of being found.

s orbital

A spherical atomic orbital; there is only one in a set or subshell.

p orbitals

A set of three orbitals that increase in size and energy as the principal quantum number increases.

d orbitals

A set of five orbitals found in the electron cloud of atoms.

Aufbau Principle

The rule stating that electrons fill the lowest energy orbitals first.

Hund's Rule

The rule stating that electrons will fill degenerate orbitals (orbitals with the same energy) singly before pairing up.

Valence Electrons

Electrons in the outermost orbitals that determine an element's reactivity.

Core Electrons

Electrons in closed shells that are very stable and do not typically participate in chemical reactions.

Atomic Radius

Half the distance between two nuclei, determined by the balance between electron-proton attraction and electron-electron repulsion.

Coulomb’s Law

The mathematical explanation for attractions between protons and electrons and repulsions between electrons ($F = \frac{k q_1 q_2}{r^2}$).

Effective Nuclear Charge ($Z_{eff}$)

The net positive charge experienced by valence electrons, calculated as the actual nuclear charge ($Z$) minus the charge screened by core electrons ($Z_{eff} = Z - S$).

Cation

A positively charged ion formed by removing the outermost electron(s) from an atom, resulting in a smaller radius.

Anion

A negatively charged ion formed by adding an electron to the lowest energy available orbital, resulting in a larger radius.

Isoelectronic Series

A group of atoms or ions that have the same electron configuration but different nuclear charges.

Ionization Energy (IE)

The energy required to remove an electron from an atom in the gas phase.