Atoms and Periodic Table Vocabulary

Vocabulary flashcards covering atomic structure, subatomic particles, atomic models, periodic table trends, and element groups.

Atom

The smallest indivisible form of an element and the basic building block of all material in the universe.

Subatomic Particles

The constituent particles of an atom, consisting of protons, neutrons, and electrons.

Proton

A positively charged subatomic particle located in the nucleus of an atom, approximately $2000$ times larger than an electron.

Neutron

A subatomic particle with no charge located in the nucleus, possessing roughly the same mass as a proton.

Electron

A small, negatively charged subatomic particle that revolves around the nucleus in electron shells.

Nucleus

The dense central region of an atom containing protons and neutrons, giving it a net positive charge.

Element

A pure material made up of only a single type of atom, whose identity is determined by the number of protons in its nucleus.

Atomic Number

The number of protons contained in the nucleus of an atom.

Mass Number

The total count of protons plus neutrons in the nucleus of an atom.

Isotopes

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

Relative Atomic Mass

The weighted average mass of all naturally occurring isotopes of an element.

Dalton's Atomic Model

A model proposed in 1808 stating that matter is composed of small, solid, indivisible particles called atoms that combine in fixed proportions.

Rutherford's Gold Foil Experiment

An experiment bombarding thin gold foil with alpha particles ($2\text{ protons} + 2\text{ neutrons}$), revealing that atoms are mostly empty space with a dense, positively charged nucleus.

Periodic Table

A visual representation of all known elements grouped according to their chemical and physical properties.

Dimitri Mendeleev

The chemist who created the periodic table by arranging elements so that their chemical properties repeated periodically, leaving gaps for undiscovered elements.

Group (Family)

A vertical column on the periodic table containing elements with similar chemical properties.

Period

A horizontal row on the periodic table across which chemical properties change gradually.

Metals

Elements located on the left side of the periodic table that are shiny, malleable, ductile, high-density, and good conductors of heat and electricity.

Non-metals

Elements located on the right side of the periodic table that lack metallic luster, are brittle as solids, and are poor conductors of heat and electricity.

Metalloids

Elements along the periodic table staircase possessing properties intermediate between metals and non-metals, frequently used as semiconductors.

Luster

The shiny appearance exhibited by freshly polished metals.

Malleability

The property of a metal allowing it to be hammered or rolled into thin sheets without breaking.

Ductility

The property of a metal allowing it to be drawn into thin wires without breaking.

Valence Electrons

The reactive electrons located in the outermost occupied shell of an atom, furthest from the nucleus and involved in chemical bonding.

Main Group Elements

Elements labeled $1A$ through $8A$ on the periodic table, where the number preceding 'A' equals the number of valence electrons.

Alkali Metals

Soft, highly reactive metals in Group 1 ($1A$), excluding hydrogen, that react when exposed to air or moisture and exist in nature only as compounds.

Alkaline Earth Metals

Malleable, reactive metals in Group 2 ($2A$) that burn when heated and occur naturally in rocks or soil as compounds.

Halogens

Soft, highly reactive non-metals in Group 17 ($7A$) that form salts and function as powerful disinfectants.

Noble Gases

Extremely stable, non-reactive non-metals in Group 18 ($8A$) with full outer electron shells, found in nature in their elemental state.

Periodicity

The repetition of a regular pattern of properties across periods in the periodic table.

Atomic Radius

The size of an atom, which generally decreases from left to right across a period and increases down a group.