Ions, Periodic Trends, and Ionic Compounds

Vocabulary flashcards covering concepts of ions, periodic trends, ionic bonding, binary ionic nomenclature, and polyatomic ionic compounds.

Ion

An atom or group of atoms with a positive or negative charge, formed strictly by gaining or losing electrons rather than protons.

Cation

A positively charged ion formed when an atom loses one or more electrons, resulting in fewer electrons than protons and a smaller radius than its neutral atom.

Anion

A negatively charged ion formed when an atom gains one or more electrons, resulting in more electrons than protons and a larger radius than its neutral atom.

Ionization Energy

The amount of energy required to remove one electron from an atom or ion in the gaseous state, following the endothermic process $\text{Atom} + \text{Energy} \rightarrow \text{Cation} + \text{Electron}$.

Electron Affinity

The amount of energy released when adding one electron to an atom or ion in the gaseous state, following the exothermic process $\text{Atom} + \text{Electron} \rightarrow \text{Anion} + \text{Energy}$.

Atomic Radius

The half-distance between nuclei in elements representing atomic size, which increases down a group and decreases from left to right across a period.

The Octet Rule

The principle stating that atoms usually react by gaining, losing, or sharing electrons to attain eight electrons in their outermost valence shell ($ns^2 np^6$), acquiring a stable electron configuration identical to a noble gas.

Alkali Metal Ion Formation

Group 1A elements with one valence electron ($ns^1$) that easily lose their outer valence shell to form stable $+1$ cations, characterized by small ionization energy and small electron affinity.

Halogen Ion Formation

Group 7A elements with seven valence electrons ($ns^2 np^5$) that easily gain one valence electron to complete their outer subshell and form stable $-1$ anions, characterized by large ionization energy and large electron affinity.

Ionic Bond

The electrostatic attraction between oppositely charged cations and anions formed through the transfer of electrons.

Crystal Lattice

A three-dimensional repeating array of cations and anions characteristic of ionic compounds.

Formula Unit

The minimum electrically neutral combination of ions in an ionic compound, described by an empirical formula with the lowest integer subscript ratios.

Binary Ionic Compound

A compound composed of two elements consisting of a metal cation and a nonmetal anion combined in ratios that yield a net zero charge.

Main Group Ionic Charge Rules

Rules for predicting charges where metals of Groups 1A, 2A, and Aluminum form positive charges equal to their Group A number ($\text{ charge} = \text{Group A number}$), and nonmetals form negative charges calculated as $\text{ charge} = \text{Group A number} - 8$.

Nonmetal Monatomic Anion Suffix (-ide)

The nomenclature rule where the standard ending of a nonmetal element name is changed to the suffix "-ide" when named as an anion (e.g., chlorine to chloride, oxygen to oxide, nitrogen to nitride).

Roman Numerals in Ionic Nomenclature

Roman numerals enclosed in parentheses placed directly after a metal ion's name to specify its positive charge when dealing with transition metals or heavier main group metals that form multiple cationic charges.

Polyatomic Ion

An ion composed of two or more atoms covalently bound that remains together as a single molecule with a net electrical charge.

Oxoanion

A polyatomic anion that contains one or more oxygen atoms bonded to a central element (e.g., $\text{SO}_4^{2-}$ or $\text{NO}_3^-$).

Ammonium Ion

The polyatomic cation $\text{NH}_4^+$ carrying a $+1$ charge, which functions as the unique polyatomic cation that replaces the metal cation in ionic compounds.

Polyatomic Compound Parentheses Rule

The rule specifying that parentheses are placed around a polyatomic ion in a formula unit only when a subscript greater than $1$ is required to balance the net electrical charge (e.g., $\text{Ca}_3(\text{PO}_4)_2$).