General Chemistry: Matter, Atomic Structure, Stoichiometry, and Nuclear Chemistry

Comprehensive vocabulary flashcards covering fundamental chemistry concepts, atomic and nuclear structure, stoichiometry, redox processes, radioactive decay, and quantum foundations of the electron.

Chemistry

The natural science that studies the composition, structure, and properties of matter, along with its transformations (chemical reactions) and the associated energy changes.

Physically Homogeneous System

A system formed by a single phase that is uniform throughout in all of its macroscopic properties, including state of aggregation, density, and color (e.g., pure liquid water).

Physically Heterogeneous System

A system consisting of two or more distinct phases separated by sharp boundary surfaces known as interfaces (e.g., water and ice, or water and oil).

Chemically Homogeneous System

A system whose chemical composition is identical and constant at every point, composed entirely of a single pure substance (e.g., pure $H_2O$).

Chemically Heterogeneous System

A system whose chemical composition varies from point to point because it is composed of two or more distinct substances (e.g., water and glucose).

Elementary Substance

A substance composed of identical atoms that display the same chemical behavior, represented by a single chemical symbol (e.g., $O_2$, $Fe$).

Compound Substance

A substance composed of atoms or ions of different chemical elements bonded together, represented by a chemical formula (e.g., $H_2O$).

Empirical Formula

A chemical formula that indicates only the types of elements present and the simplest whole-number numerical ratio of their atoms (e.g., $CH_2O$).

Molecular Formula

A chemical formula that provides the composition of the empirical formula plus the exact number of atoms of each element that compose a molecule (e.g., $C_6H_{12}O_6$).

Structural Formula

A chemical representation showing the exact connectivity, bonds, and spatial arrangement of atoms or ions within a molecule.

Nuclide

A specific atomic species defined by an exact atomic number $Z$ (number of protons) and mass number $A$ (sum of protons and neutrons), written as $^A_Z E$.

Proton ($p^+$)

A subatomic particle located in the atomic nucleus with a positive charge of $q = 1.6022 \times 10^{-19}\text{ C}$ and a mass of approximately $m = 1.6726 \times 10^{-27}\text{ kg}$.

Neutron ($n$)

An uncharged subatomic nuclear particle with an electrical charge of $q = 0\text{ C}$ and a mass of approximately $m = 1.6726 \times 10^{-27}\text{ kg}$.

Electron ($e^-$)

A subatomic particle moving in the space around the nucleus with a negative charge equal and opposite to that of the proton ($q = -1.6022 \times 10^{-19}\text{ C}$) and a mass of $m = 9.109 \times 10^{-31}\text{ kg}$.

Isotopes

Atoms of the same chemical element sharing the same atomic number $Z$ (and thus identical chemical behavior) that differ in their mass number $A$ due to differing numbers of neutrons.

Relative Isotopic Abundance ($P_{AE}$)

The percentage or fraction with which a specific isotope of an element is found in nature relative to the total number of all isotopes of that element: $P_{AE} = \frac{N_{AE}}{N_{tot_E}} \times 100\%$.

Atomic Mass Unit (u.m.a.)

A mass standard defined as exactly $\frac{1}{12}$ of the mass of a single carbon-12 ($^{12}C$) atom, which equals $1.6606 \times 10^{-24}\text{ g}$.

Average Atomic Mass

The weighted average of the atomic masses of all natural isotopes of an element based on their relative natural abundance, expressed in atomic mass units.

Avogadro's Number ($N_A$)

A fundamental constant indicating the exact number of elementary particles contained in one mole of any substance, equal to $6.022 \times 10^{23}$.

Molar Mass ($MM$)

The mass in grams of one mole of a substance ($\text{g/mol}$), which is numerically equivalent to the substance's relative atomic or formula mass.

Oxidation Number (O.N.)

The formal charge assigned to an atom in a compound when all bonding electrons are arbitrarily allocated to the more electronegative element involved in each bond.

Oxidation

The half-reaction process involving the loss of electrons by a chemical species ($E \rightarrow E^{+n} + n e^{-}$), resulting in an increase in its oxidation number.

Reduction

The half-reaction process involving the acquisition of electrons by a chemical species ($X + n e^{-} \rightarrow X^{-n}$), resulting in a decrease in its oxidation number.

Limiting Reactant

The reactant that is completely consumed first in a chemical reaction because it has the lowest ratio of molar quantity to its stoichiometric coefficient ($\frac{n_x}{\text{coeff}}$).

Reaction Yield

The percentage ratio of the actual molar amount of product obtained experimentally to the theoretical maximum amount calculated from stoichiometry: $\eta_P = \frac{n_{\text{actual}}}{n_{\text{theoretical}}} \times 100\%$.

Strong Nuclear Force

The powerful attractive nuclear force that binds protons and neutrons together in the atomic nucleus, overcoming the electrostatic Coulomb repulsion between positively charged protons.

Segrè Diagram

A plot of neutron number ($N = A - Z$) on the y-axis against proton number ($Z$) on the x-axis, illustrating the band of stable nuclides and predicting nuclear decay paths.

Alpha Decay ($\alpha$)

A radioactive decay mode typical of very heavy nuclei ($Z > 82$) in which the nucleus ejects an alpha particle ($^4_2\alpha$), drastically reducing both its mass number and atomic number.

Beta-Minus Decay ($\beta^-$)

A radioactive decay mode typical of neutron-rich nuclei located above the stability band, wherein a neutron converts into a proton while emitting a high-speed electron ($\beta^-$), increasing $Z$ by $1$.

Beta-Plus Decay ($\beta^+$)

A radioactive decay mode typical of proton-rich nuclei located below the stability band, where a proton converts into a neutron while emitting a positron ($\beta^+$), decreasing $Z$ by $1$.

Gamma Emission ($\gamma$)

A de-excitation process in which an excited daughter nucleus releases excess energy via the emission of a very high-energy photon without altering its atomic or mass numbers.

Radioactive Activity ($A$)

The number of atomic decays occurring per unit time ($A = \frac{dN}{dt} = \lambda \cdot N$), measured in Becquerels ($\text{Bq}$), where $1\text{ Bq} = 1\text{ decay/s}$.

Half-Life ($t_{1/2}$)

The characteristic time required for the number of undecayed radioactive atoms in a sample to decrease to exactly half of its initial value: $t_{1/2} = \frac{\ln(2)}{\lambda}$.

Wave-Particle Duality

The principle formulated by Louis de Broglie asserting that all moving matter possesses wave-like properties alongside particulate properties, related by the equation $p = \frac{h}{\lambda}$.

Davisson-Germer Experiment

The experiment confirming the wave nature of matter by demonstrating that a beam of electrons passing through the crystal lattice of nickel produces wave interference patterns.

Wave Function ($\Psi$)

A mathematical function that describes the amplitude and behavior of an electron wave across space and time as a solution to the Schrödinger equation.