Atomic Structure, Periodic Trends, and Chemical Bonding

Comprehensive vocabulary flashcards covering atomic structure, ionic and covalent bonding, periodic table history, group classifications, and periodic trends.

Ion

An atom or group of atoms that has gained at least one electron to become negatively charged (anion) or lost at least one electron to become positively charged (cation).

Ionic Bond

The strong electrostatic force of attraction between oppositely charged metal cations and non-metal anions.

Cation

A positively charged ion formed when an atom loses one or more valence electrons.

Anion

A negatively charged ion formed when an atom gains one or more valence electrons.

Electrostatic Force

A non-contact attractive or repulsive force caused by electric charges on particles.

Giant Ionic Lattice

A regular, repeating three-dimensional structure formed by strong electrostatic attractions extending in all directions between oppositely charged ions.

Giant Covalent Structure

A macromolecular lattice formed exclusively by non-metal atoms joined through shared pairs of electrons, typically insoluble in water and non-conductive (with exceptions such as graphite).

Graphite

A giant covalent allotrope of carbon that conducts electricity because it possesses delocalized electrons that are free to move between its layers.

Covalent Bond

A chemical bond formed when two non-metal atoms share one or more pairs of electrons to achieve a stable electron configuration.

Molecule

A neutral particle formed when two or more atoms join together chemically through covalent bonds.

Element

A pure chemical substance consisting of only one type of atom that cannot be broken down into simpler substances by chemical reactions.

Compound

A substance formed when atoms of two or more different elements chemically combine in fixed ratios, exhibiting physical and chemical properties distinct from its constituent elements.

Stable Atom

An atom that possesses a complete valence shell (typically $8$ electrons, or $2$ for helium) and does not readily gain, lose, or share electrons.

Reactive Atom

An atom with an incomplete valence shell that tends to share, gain, or lose electrons to achieve chemical stability.

Dot and Cross Diagram

A structural drawing used to illustrate chemical bonding where dots represent valence electrons originating from one atom and crosses represent those from another.

Diatomic Molecule

A molecule composed of exactly two atoms chemically bonded together, such as $Cl_2$, $O_2$, or $H_2$.

Intermolecular Forces

The forces of attraction that exist between separate covalently bonded molecules.

Double Covalent Bond

A covalent linkage formed when two atoms share two pairs ($4$ electrons total) of electrons, as exemplified by the $O_2$ molecule.

Periodic Table

A comprehensive organizational chart of all discovered chemical elements arranged by increasing atomic number and recurring chemical properties.

Antoine Lavoisier

French chemist who in $1789$ laid the foundation of modern elemental classification by identifying and naming chemical elements, naming hydrogen, and discovering in $1772$ that diamonds are composed of carbon.

John Dalton

English meteorologist and chemist who introduced modern atomic theory in the early 1800s ($1803$), proposing that all matter is composed of tiny indivisible particles called atoms.

Johann Wolfgang Döbereiner

German physicist who in $1829$ classified chemically similar elements into groups of three called triads, noting that the average atomic mass of the lightest and heaviest elements approximated that of the middle element.

Law of Octaves

A periodic classification proposed by John Newlands in $1864$ stating that when elements are arranged by increasing atomic mass, every eighth element exhibits similar chemical properties.

Dmitri Mendeleev

Russian chemist who formulated the first periodic table in $1869$ by organizing elements according to atomic mass and properties, leaving intentional gaps and accurately predicting undiscovered elements.

Henry Moseley

English physicist who in $1913$ rearranged the elements on the periodic table in order of increasing atomic number rather than atomic mass.

Glenn T. Seaborg

American nuclear chemist who expanded the periodic table by establishing a separate section for synthetic transuranic elements produced in laboratories.

Atomic Number

The total number of protons located within the nucleus of an atom, serving as a distinct unique identifier for each chemical element.

Atomic Mass

The combined mass of the protons and neutrons inside an atom's nucleus, often expressed as an average value accounting for isotopic abundance.

Isotopes

Variants of a particular chemical element that possess identical numbers of protons but differing numbers of neutrons within their atomic nuclei.

Period

A horizontal row in the periodic table; all elements in a given period possess the same number of occupied electron shells.

Group

A vertical column in the periodic table containing elements with the same number of valence electrons and similar chemical behavior.

Electron Shell Capacity Formula

The mathematical formula $2n^2$ used to calculate the maximum electron capacity of an atomic shell, where $n$ denotes the principal quantum number (shell level).

Alkali Metals

The highly reactive chemical elements comprising Group $1$ (excluding hydrogen) with $1$ valence electron, characterized by low density, softness, and vigorous reactions with water to yield alkaline hydroxides.

Halogens

The reactive non-metallic elements of Group $7$ (Group $17$) with $7$ valence electrons, which exist as diatomic molecules in their elemental state and react with metals to form halide salts.

Noble Gases

The unreactive, monatomic, colourless, and odourless gases comprising Group $8$ (Group $18$) characterized by completely filled valence shells.

Metalloid

An element possessing physical and chemical properties intermediate between those of metals and non-metals, being semiconductors of heat and electricity.

Allotropes

Different physical or structural forms of the same chemical element in the same physical state, such as diamond and graphite for carbon.

Ionization Energy

The amount of energy required to remove an electron from an atom in its gaseous state; increases across a period from left to right.

Electronegativity

The chemical property describing the relative tendency or ability of an atom to attract shared electrons toward itself; increases across a period from left to right.

Atomic Radius Trend

The systematic variation in atomic size, which decreases across a period from left to right due to increased nuclear attraction, and increases down a group due to the addition of electron shells.