Chapter 4: From Elements to Compounds

Flashcards providing comprehensive vocabulary coverage for Chapter 4: From Elements to Compounds, including periodic trends, ionic and covalent bonding, nomenclature, polyatomic ions, and solution properties.

Ionic Compound

A neutral compound formed when atoms transfer electrons—where metals lose electrons to become cations and nonmetals gain electrons to become anions—causing oppositely charged ions to stick together.

Covalent Compound

A compound formed when two or more nonmetal atoms form connections by sharing pairs of valence electrons.

Effective Nuclear Charge ($Z_{\text{eff}}$)

A measure of how tightly valence electrons are attracted to the nucleus, calculated as the nuclear charge ($Z$) minus the number of core shielding electrons ($S$): $Z_{\text{eff}} = Z - S$.

Electron Shielding ($S$)

The repulsive barrier provided by inner (core) electrons that reduces the full electrostatic pull of the nucleus felt by outer valence electrons.

Cation

A positively charged ion formed when an atom (typically a metal) loses one or more electrons.

Anion

A negatively charged ion formed when an atom (typically a nonmetal) gains one or more electrons.

Ionic Radius of a Cation

The size of a positively charged ion, which is always smaller than its neutral parent atom due to the loss of outer electrons and an increased effective nuclear attraction.

Ionic Radius of an Anion

The size of a negatively charged ion, which is always larger than its neutral parent atom due to increased electron-electron repulsions in the valence shell.

Isoelectronic Series

A group of atoms and ions that possess the exact same electron configuration and number of electrons (e.g., $S^{2-}$, $Cl^-$, $Ar$, and $K^+$).

Ionization Energy ($IE$)

The amount of energy required to remove an electron from a gaseous atom or ion to form a cation (e.g., $Li(g) \rightarrow Li^+(g) + e^-$).

Successive Ionization Energies

The energies required to remove electrons one after another from an atom ($IE_1 < IE_2 < IE_3$), showing a drastic increase when removing core electrons compared to valence electrons.

Electron Affinity ($EA$)

The energy change associated with the addition of an electron to a gaseous atom to form an anion; a negative value indicates that energy is released and the resulting anion is stabilized.

Lewis Dot Symbol

A notation showing the elemental symbol surrounded by dots representing its valence electrons, used to track valence electron counts and predict ion formation.

Octet Rule

The principle that atoms tend to gain, lose, or share electrons in order to achieve a stable arrangement of eight valence electrons, matching a noble gas configuration.

Stock System

A system of chemical nomenclature for transition metal cations that indicates the positive charge using Roman numerals in parentheses (e.g., iron(II) for $Fe^{2+}$ and iron(III) for $Fe^{3+}$).

Polyatomic Ion

A group of covalently bonded atoms that carries an overall net positive or negative electrical charge.

Oxyanion

A polyatomic anion containing one or more oxygen atoms bonded to another nonmetal atom, typically named with the suffix '-ate' for more oxygens and '-ite' for fewer oxygens.

Salt

A general term for any neutral ionic compound formed by an organized array of cations and anions balancing each other's charges.

Ionic Bond

The strong electrostatic force of attraction that holds oppositely charged cations and anions together in a crystal lattice.

Coulomb's Law

A mathematical relationship ($F_e = k_e \frac{|q_1 q_2|}{r^2}$) stating that the attractive force between ions is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

Lattice Energy

A measure of the bond strength in an ionic compound, directly related to the electrostatic force of attraction between the ions in the crystal lattice.

Hydrate

An ionic solid that contains water molecules trapped inside its crystal lattice in a specific, fixed stoichiometric ratio (e.g., $NiCl_2 \cdot 6H_2O$).

The Magnificent Seven

The seven nonmetal elements that naturally exist as homonuclear diatomic molecules: hydrogen ($H_2$), nitrogen ($N_2$), oxygen ($O_2$), fluorine ($F_2$), chlorine ($Cl_2$), bromine ($Br_2$), and iodine ($I_2$).

Lewis Structure

A structural representation of a molecule or polyatomic ion showing how valence electrons are arranged as bonding pairs (lines) and lone pairs (dots).

Bonding Pair

A pair of valence electrons shared between two atoms in a covalent bond (representing a single bond of 2 electrons, double bond of 4 electrons, or triple bond of 6 electrons).

Lone Pair (Nonbonding Pair)

A pair of valence electrons localized on a single atom that is not involved in covalent bonding.

Duet Rule

The bonding rule specific to hydrogen, stating that it attains a stable valence electron configuration by sharing electrons to achieve a total of only two electrons (like helium).

Solution

A homogeneous mixture formed when a solid (such as salt or sugar) dissolves and disperses uniformly throughout a liquid solvent.

Dissociation

The process by which an ionic solid breaks apart into its individual mobile cations and anions when dissolved in water (e.g., $NaCl(s) \rightarrow Na^+(aq) + Cl^-(aq)$).