Atomic Theory, Electron Configurations, and Periodic Trends

Vocabulary flashcards covering atomic structure, subatomic particles, Rutherford and Bohr atomic models, Coulomb's Law, isotopes, electron configurations, and periodic trends.

Electron Configuration

The arrangement of electrons into the energy levels, sublevels, and orbitals of an atom.

Aufbau Principle

The principle stating that electrons are added one at a time to the lowest available energy level until all are accounted for.

Pauli Exclusion Principle

The rule stating that an orbital can hold a maximum of 2 electrons, which must have opposite spins (one spin up $\uparrow$, one spin down $\downarrow$).

Hund's Rule

The rule stating that electrons will fill all equal energy orbitals singly before pairing up, remaining unpaired unless necessary because pairing requires energy.

Atomic Number

The number of protons in the nucleus of an atom, which is equal to the nuclear charge and defines the identity of the chemical element.

Mass Number

The sum of the protons and neutrons ($p^+ + n^0$) in an atom or isotope's nucleus, representing the mass of that specific nucleus.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Atomic Mass

The weighted average mass number of an element's naturally occurring isotopes, expressed in atomic mass units ($\text{amu}$).

Mass Spectrometer

An instrument that separates an element sample into light and heavy isotopic lines according to relative mass and relative abundance.

Ion

An atom that has acquired an electrical charge by gaining or losing electrons, calculated as $\text{charge} = \#p^+ - \#e^-$.

Oxidation

The process involving the loss of one or more electrons by an atom or ion.

Reduction

The process involving the gain of one or more electrons by an atom or ion.

Alpha Rays

Heavy, positively charged radiation particles emitted during radioactive decay, consisting of 2 protons and 2 neutrons ($2p^+$, $2n^0$).

Beta Rays

Radiation consisting of lightweight, negatively charged particles that are high-speed electrons ($e^-$).

Gamma Rays

A form of penetrating electromagnetic radiation consisting of high-energy light (such as X-rays) without mass or charge.

Rutherford's Gold Foil Experiment

An experiment demonstrating that most alpha particles pass undeflected through gold foil while a few deflect, proving the atom is mostly empty space with a tiny, dense, positively charged nucleus.

Coulomb's Law

The physical law stating that the electrostatic force between two charged objects is given by $F = k \frac{q_1 q_2}{d^2}$, being proportional to charge magnitudes and inversely proportional to the square of the distance between them.

Periodic Trend

A repeating pattern of physical or chemical characteristics that recurs across rows (periods) or down columns (families) of the periodic table.

Atomic Radius

The size or radius of an atom, measured from the nucleus to the outermost occupied electron orbital; increases down a family and decreases across a period.

Ionization Energy

The energy cost (measured in $\text{J/mole}$) required to completely remove an electron from an atom; decreases down a group and increases across a period.

Electron Affinity

The energy change (in $\text{J/mole}$) that occurs when an electron is added to an atom, which can be negative (releasing energy) or positive (requiring energy).

Electronegativity

The ability of an atom to attract electrons within a chemical bond, reflecting how effectively its nucleus can draw in valence electrons from an adjacent atom.

Octet Rule

The tendency of atoms to gain or lose electrons in order to achieve a full valence shell of 8 electrons, mimicking the electron configuration of the nearest noble gas.

Excited State

An unstable, high-energy state where electrons have absorbed specific quanta of energy and moved to orbitals farther from the nucleus.

Ground State

The lowest, most stable energy configuration of an atom where electrons occupy their standard, lowest-energy available orbitals.

Quantized

A condition in which a physical property, such as electron energy levels, can only possess discrete, specific values rather than a continuous spectrum.

Core Notation

A shorthand method of writing electron configurations where the configuration of the preceding noble gas is placed in brackets, followed by the remaining valence sublevels.

Valence Electrons

The outermost electrons occupying the highest energy level ($s$ and $p$ sublevels) that participate in chemical bonding and reactions.

Deuterium ($^2\text{H}$)

An isotope of hydrogen with a mass number of $2$, containing 1 proton and 1 neutron in its nucleus.

Tritium ($^3\text{H}$)

A radioactive isotope of hydrogen with a mass number of $3$, containing 1 proton and 2 neutrons in its nucleus.