Atomic Structure and Models: Protons, Neutrons, Electrons & Periodic Table Study Guide | Quizlet

Proton

A positively charged subatomic particle located in the nucleus of an atom with a mass of approximately $1\,\text{amu}$.

Neutron

A neutral subatomic particle with no electric charge, located in the nucleus of an atom, with a mass of approximately $1\,\text{amu}$.

Electron

A negatively charged subatomic particle located outside the nucleus in energy levels or orbitals, with negligible mass.

Atomic Structure

The arrangement of subatomic particles within an atom, consisting of a dense central nucleus surrounded by electrons.

Nucleus

The small, dense, positively charged center of an atom containing protons and neutrons.

Periodic Table

A tabular arrangement of chemical elements organized by increasing atomic number, recurring electron configurations, and chemical properties.

Atomic Number

The number of protons in the nucleus of an atom, represented by the symbol $Z$, which uniquely identifies a chemical element.

Mass Number

The total count of protons and neutrons in the nucleus of an atom, represented by the symbol $A$.

Isotope

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

Valence Electrons

The electrons in the outermost shell or energy level of an atom that participate in chemical bonding.

Dalton's Atomic Model

The solid sphere model proposing that matter is composed of indivisible, indestructible atoms of specific elements.

Thomson's Atomic Model

The plum pudding model proposing that negatively charged electrons are embedded within a positively charged sphere.

Rutherford's Atomic Model

The nuclear model demonstrating that an atom is mostly empty space with a small, dense, positively charged nucleus at the center.

Bohr's Atomic Model

The planetary model stating that electrons travel around the nucleus in specific circular orbits with fixed energy levels.

Quantum Mechanical Model

The modern electron cloud model describing electrons as existing in probabilistic regions called orbitals rather than fixed paths.

Ion

An atom or group of atoms that has acquired a net electric charge by gaining or losing one or more electrons.

Cation

A positively charged ion formed when a neutral atom loses one or more electrons.

Anion

A negatively charged ion formed when a neutral atom gains one or more electrons.

Group (Periodic Table)

A vertical column on the periodic table containing elements that share similar chemical properties and the same number of valence electrons.

Period (Periodic Table)

A horizontal row on the periodic table indicating the total number of occupied electron shells in an element's atoms.

Subatomic Particles

The fundamental constituents of an atom, consisting of protons, neutrons, and electrons.

Atomic Mass Unit (amu)

A standard unit of mass defined as one-twelfth of the mass of an unbound neutral carbon-12 atom.

Energy Levels

Fixed regions located at specific distances from the nucleus where electrons are permitted to orbit or reside.

Neutral Atom

An atom in which the number of protons equals the number of electrons, resulting in zero overall electrical charge.

Electron Cloud

The region around an atom's nucleus where electrons are most likely to be located according to quantum probabilities.