Chemistry 119 - Chapter 2: Orbital Shapes, Energies, Electron Spin, and Pauli Principle

Vocabulary flashcards defining fundamental quantum mechanical concepts, orbital types, magnetic properties, polyelectronic principles, and rules for writing electron configurations based on Chapter 2.

Bohr model

An early atomic model based on electron shells that only accurately describes hydrogen atoms.

Wavefunction square ($\psi^2$)

The mathematical square of an electron's wavefunction that defines the orbital shape by giving the probability distribution of finding an electron in space.

s-orbital

A spherically shaped orbital extending radially from the nucleus, characterized by angular quantum numbers $l = 0$ and $m_l = 0$, containing $n - 1$ spherical nodes.

Spherical node

A spherical surface surrounding the nucleus where the probability of finding an electron is zero.

p-orbitals

A set of three degenerate orbitals ($l = 1$) oriented along the x, y, and z axes at $90^\text{o}$ angles to one another.

d-orbitals

A set of five degenerate orbitals ($l = 2$) characterized by having two nodal planes.

Diamagnetic substance

A substance in which all electrons are paired, causing it not to be attracted to a magnetic field.

Paramagnetic substance

A substance containing unpaired electrons that is attracted to a magnetic field.

Electron spin quantum number ($m_s$)

A quantum number describing the intrinsic spin orientation of an electron, taking values of $m_s = +\frac{1}{2}$ (spin up) or $m_s = -\frac{1}{2}$ (spin down).

Pauli exclusion principle

A principle formulated by Wolfgang Pauli in 1925 stating that no two electrons in the same atom can possess identical sets of four quantum numbers ($n$, $l$, $m_l$, $m_s$).

Penetration effect

The ability of an electron in an s orbital to approach closer to the nucleus than an electron in a p orbital of the same shell, making the s orbital lower in energy.

Effective nuclear charge ($Z^*$)

The net positive charge experienced by an electron in a polyelectronic atom, calculated as $Z^* = Z - S$, where $Z$ is the atomic number and $S$ is the screening constant.

Aufbau principle

The conceptual procedure of building up an atom's electron configuration by filling orbitals in order of increasing energy, from lowest to highest.

Hund's rule

The principle stating that degenerate orbitals must each be occupied by one electron with parallel spin before any orbital is doubly occupied.

Valence electrons

The electrons in the outermost electron shell of an atom that participate in chemical bonding and reactivity.

Core electrons

The inner-shell electrons of an atom that correspond to a completed noble gas electron configuration.

Stern-Gerlach experiment

An experiment passing silver atoms through an inhomogeneous magnetic field that split the beam into two paths, proving the quantization of electron spin.