Chapter 2: Atomic Structure and Radioisotopes

Vocabulary flashcards reviewing core topics from Chapter 2, including atomic structure, isotopes, periodic table organization, electron arrangements, radioactive decay, and properties of radiation.

Classification of Matter

Matter is categorized into Pure Substances (Elements and Compounds) and Mixtures (Homogeneous and Heterogeneous).

Subatomic Particles

The constituent particles of an atom: Protons ($1+$ charge, mass $1.67 \times 10^{-24}\,\text{g}$ or $1.007\,\text{amu}$, located in nucleus), Neutrons ($0$ charge, mass $1.67 \times 10^{-24}\,\text{g}$ or $1.008\,\text{amu}$, located in nucleus), and Electrons ($1-$ charge, mass $9.11 \times 10^{-28}\,\text{g}$ or $0.00055\,\text{amu}$, located in electron orbitals).

Atomic Number ($Z$)

The total number of protons present in the nucleus of an atom, defining its chemical identity on the periodic table.

Mass Number ($A$)

The total count of protons and neutrons contained within the nucleus of an atom.

Isotope Symbol Notation

A standard chemical representation ${}_Z^A\text{X}$, where $\text{X}$ is the elemental symbol, $A$ is the mass number, and $Z$ is the atomic number.

Isotope

Atoms of the same element that share the same atomic number (protons) but possess different mass numbers due to a differing number of neutrons.

Average Atomic Mass

The weighted average mass of naturally occurring atoms that compose an element based on isotopic percent natural abundance.

Period (Periodic Table)

A horizontal row on the periodic table where elements are arranged in increasing order of atomic number.

Group (Periodic Table)

A vertical column on the periodic table composed of elements sharing similar physical and chemical properties, designated as Group A (main group) or Group B (transition elements).

Metals

Elements that are shiny, malleable, ductile, and good conductors of heat and electricity, existing as solids at room temperature with the exception of mercury ($\text{Hg}$).

Nonmetals

Elements that are dull, brittle, and poor conductors of heat and electricity (insulators), existing as solids, liquids, or gases at room temperature.

Metalloids

Elements (also known as semi-metals) displaying properties intermediate between metals and nonmetals.

Valence Electrons

Electrons residing in the highest principal energy level ($n$) of an atom.

Periodicity

The occurrence of recurring physical and chemical trends across elements when ordered by atomic number.

Radioisotope

An isotope containing an unstable nucleus that undergoes spontaneous decay to emit radiation and reach a stable configuration.

Alpha ($\alpha$) Particle

A slow-moving, high-energy particle comprised of two protons and two neutrons (${}_2^4\alpha$) bearing a $+2$ charge.

Alpha Decay Equation

A nuclear process represented as $\text{Parent Nuclide} \rightarrow \text{Daughter Nuclide} + \alpha\,\text{Particle}$ (e.g., ${}_{88}^{223}\text{Ra} \rightarrow {}_{86}^{219}\text{Rn} + {}_2^4\alpha$).

Beta ($\beta$) Particle

A high-energy electron ejected from an unstable nucleus during radioactive decay, represented as ${}_{-1}^0\beta$.

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

The duration of time required for half ($\frac{1}{2}$) of the parent nuclides in a radioactive sample to decay into daughter nuclides.

Fraction Remaining Formula

The mathematical formula $N = \left(\frac{1}{2}\right)^n$ used to determine the remaining fraction ($N$) of a radioisotope after $n$ half-lives.

Electromagnetic Radiation

Energy moving through space as a wave, defined by $\text{Energy} (E) = h\nu = \frac{hc}{\lambda}$.

Metastable State

An excited, high-energy state of a daughter nuclide denoted by 'm' that releases a gamma ray (${}_0^0\gamma$) to form a lower-energy stable atom.

Ionizing Radiation

High-energy radiation capable of dislodging valence electrons from atoms, including $\alpha$, $\beta$, $\gamma$, x-rays, and high-energy UV radiation.

Penetrating Power of Radiation

A measure of how deeply radiation passes into matter, sequentially blocked by paper ($\alpha$), aluminum ($\beta$), thin lead (x-ray), and thicker lead ($\gamma$).

Gray (Gy)

The SI unit of absorbed dose measuring the total radiation energy absorbed by an individual.

Sievert (Sv)

The SI unit of effective dose quantifying biological damage caused by radiation based on both energy and penetrating power.