Atoms, Elements, and Nuclear Radiation

Vocabulary flashcards covering the structure of the atom, periodic trends, elements, subatomic particles, and principles of nuclear radiation, decay, fission, and fusion.

Element

A pure substance that cannot be broken down into simpler substances by ordinary laboratory processes and serves as a fundamental building block of matter.

Chemical Symbol

A one- or two-letter abbreviation that represents the name of an element, beginning with a capital letter.

Group

A vertical column on the periodic table containing elements that share similar physical and chemical properties.

Period

A horizontal row of elements on the periodic table.

Representative Elements

Elements designated with the letter A (Groups 1A through 8A) on the periodic table.

Transition Elements

Elements designated with the letter B (Groups 3B through 12B) located in the center block of the periodic table.

Alkali Metals

Elements belonging to Group 1A on the periodic table, including lithium, sodium, potassium, rubidium, and cesium.

Halogens

Elements belonging to Group 7A on the periodic table, including fluorine, chlorine, bromine, and iodine.

Metal

An element located to the left of the heavy zigzag line on the periodic table that is shiny, ductile, and a good conductor of heat and electricity.

Nonmetal

An element located to the right of the zigzag line on the periodic table that is typically dull, brittle, a poor conductor, and a good insulator.

Metalloid

An element located along the heavy zigzag line exhibiting intermediate properties between metals and nonmetals, used as semiconductors and insulators.

Proton

A subatomic particle located in the nucleus of an atom that possesses a positive ($+$) electrical charge.

Neutron

A subatomic particle located in the nucleus of an atom that has mass but possesses no electrical charge (neutral).

Electron

A subatomic particle that carries a negative ($-$) charge and occupies the large, empty space surrounding the atomic nucleus.

Atomic Mass Unit (amu)

A unit of mass defined as equal to exactly $1/12$ of the mass of a carbon-12 atom.

Atomic Number

A number specific to each element, equal to the number of protons in the nucleus of an atom, that appears above the element's symbol on the periodic table.

Mass Number

The total number of protons and neutrons in an atom's nucleus, which is always a whole number and does not appear on the periodic table.

Isotopes

Atoms of the same element that contain the same number of protons but different numbers of neutrons, giving them different mass numbers.

Atomic Mass

The weighted average of the masses of all naturally occurring isotopes of an element, displayed with two decimal places below the chemical symbol on the periodic table.

Atomic Spectrum

A unique series of distinct lines of color produced when light from an element that has been heated passes through a prism.

Valence Electrons

Electrons situated in the outermost energy level of an atom, corresponding to the group number for representative elements.

Lewis Structure (Electron-Dot Symbol)

A visual notation representing the valence electrons of an atom as dots placed around its chemical symbol.

Atomic Radius

The distance between the nucleus and the outermost electrons, which increases down a group and decreases across a period from left to right.

Ionization Energy

The amount of energy required to remove one of the outermost electrons from an atom in its gaseous state.

Metallic Character

The property describing an element's ability to lose electrons easily, which is higher in metals on the left side of the periodic table and increases down a group.

Radioactive Isotope (Radioisotope)

An isotope with an unstable nucleus that spontaneously emits radiation to transition into a more stable nuclear state.

Nuclear Radiation

The spontaneous release of small particles or rays of energy emitted from an unstable nucleus to achieve stability.

Alpha ($\alpha$) Particle

A form of radiation comprising two protons and two neutrons ($^4_2\text{He}$) with a mass number of $4$ and a charge of $2+$.

Beta ($\beta$) Particle

A high-energy electron ($^0_{-1}e$) emitted from the nucleus when a neutron breaks down into a proton, carrying a charge of $1-$.

Positron ($\beta^+$)

A positively charged electron ($^0_{+1}e$) emitted from the nucleus when a proton is converted into a neutron, carrying a charge of $1+$.

Gamma ($\gamma$) Ray

High-energy radiation ($^0_0\gamma$) with zero mass number and zero charge released from an unstable nucleus during radioactive decay.

Transmutation

The process of converting a stable nucleus into a radioactive nucleus by bombarding it with a small particle.

Geiger Counter

A radiation-measuring instrument that detects beta and gamma radiation by using ions produced by radiation to create an electrical current.

Curie (Ci)

A unit of radiation that measures activity as the number of atoms decaying in $1\text{ second}$.

rad (Radiation Absorbed Dose)

A radiation unit measuring the amount of radiation energy absorbed by the tissues of the body.

rem (Radiation Equivalent)

A radiation unit measuring the biological damage produced in tissues by different types of radiation.

$$\text{LD}_{50}$$

The whole-body radiation dose that represents the lethal dose expected to cause death in $50\%$ of an exposed population.

Half-Life

The time required for the radiation level or active amount of a radioisotope sample to decrease to one-half of its initial value.

Nuclear Fission

A nuclear process in which a large nucleus bombarded with a small particle splits into smaller nuclei and several neutrons while releasing large amounts of energy.

Nuclear Chain Reaction

A self-sustaining series of nuclear fissions where neutrons released from each splitting nucleus strike and split neighboring fissionable nuclei.

Critical Mass

The minimum quantity of fissionable material required to sustain a continuous nuclear chain reaction.

Control Rods

Components placed inside a nuclear reactor that absorb neutrons to regulate and slow the rate of the fission chain reaction.

Nuclear Fusion

A nuclear process occurring at extremely high temperatures ($100\,000\,000\,^\circ\text{C}$) in which small nuclei combine into a larger nucleus, releasing massive quantities of energy.