Unit 2: Chemical Bonding and Interactions

Vocabulary practice flashcards covering atomic history, periodic trends, separation techniques, ionic and covalent bonding, Lewis structures, VSEPR geometries, and intermolecular forces from Unit 2.

Atom

The smallest particle of a chemical that can exist; the basic unit of an element that cannot be divided by chemical means.

Element

A substance that is made up of only one type of atom.

Compound

A substance made up of atoms of different elements that are chemically bonded together.

Pure Substance

Matter that has the same chemical composition throughout (an element or a compound).

‘Atomos’

The Greek word meaning 'uncuttable' or 'indivisible,' coined by Democritus in 400 B.C. for particles that cannot be divided further and whose shapes and sizes determine the properties of matter.

Plum Pudding Model

An atomic model proposed by J.J. Thomson depicting a positively charged sphere with negatively charged electrons dotted throughout.

Nuclear Model

An atomic model proposed by Ernest Rutherford in 1918 suggesting that the atom is mostly empty space with a small, dense, positively charged nucleus surrounded by an electron cloud.

Bohr Model

A model introduced by Niels Bohr in 1913 where electrons travel only in specific circular paths or shells around the nucleus, each possessing different energy levels based on its distance from the nucleus.

Alpha Scattering Experiment

An experiment where positively charged alpha ($\alpha$) particles were fired at gold foil, showing that most passed straight through while a very small percentage bounced backward, proving the existence of a dense, positive nucleus.

Nucleus

The central part of an atom containing protons ($+$ charge) and neutrons (no charge), which have the same mass and make up most of the atom's mass.

Groups (Periodic Table)

The vertical columns on the periodic table that indicate the number of electrons in the outer shell for main group elements.

Periods (Periodic Table)

The horizontal rows on the periodic table that indicate the total number of electron shells an atom has.

Mixture

A combination consisting of two or more pure substances that may vary in composition.

Homogeneous Mixture

A mixture with particles distributed uniformly throughout, often referred to as a solution.

Heterogeneous Mixture

A mixture that does not have uniform composition throughout (such as sand in water or mud).

Solute

The substance in a solution that is present in the lesser amount.

Solvent

The substance in a solution that is present in the greater amount.

Saturated Solution

A solution that contains as much dissolved solid as it can possibly hold.

Crystallization

A separation technique based on solubility used to separate a dissolved solid from a liquid by heating the solution to evaporate solvent, forming a saturated solution, and cooling it to allow crystals to grow.

Filtration

A separation technique based on particle size and solubility used to separate an insoluble solid from a liquid solvent using filter paper and a funnel.

Filtrate

The liquid that passes through the filter paper into the container during filtration.

Residue

The solid material that remains trapped in the filter paper during filtration.

Distillation

A separation technique based on differences in boiling points used to separate a solvent from a solution by evaporating the liquid, cooling the vapor in a condenser, and collecting the pure distillate.

Alkali Metals

Elements belonging to Group 1A on the periodic table that are very reactive with other elements and compounds.

Alkaline Earth Metals

Elements belonging to Group 2A on the periodic table that are less reactive than alkali metals but more reactive than transition metals.

Halogens

Elements belonging to Group 7A on the periodic table that naturally occur as diatomic molecules (e.g., $F_2$, $Cl_2$, $Br_2$, $I_2$).

Diatomic Molecule

A molecule consisting of two of the exact same atoms chemically bonded together.

Noble Gases

Elements belonging to Group 8A on the periodic table that do not react with anything and are very stable.

Ion

A charged atom with an unequal number of protons and electrons resulting from the loss or gain of electrons.

Cation

A positively charged ion formed when an atom loses electrons, resulting in fewer electrons than protons.

Anion

A negatively charged ion formed when an atom gains electrons, resulting in more electrons than protons.

Monatomic Ion

An ion consisting of a single atom (e.g., $Cl^-$, $O^{2-}$, $N^{3-}$).

Polyatomic Ion

An ion composed of two or more atoms that has a specific name, formula, and overall charge assigned to it (e.g., $SO_4^{2-}$, $NO_3^-$).

Ionic Compound

A compound composed of a metal cation and a nonmetal anion held together in a stable crystal lattice by electrostatic attraction.

Covalent Compound

A molecular compound composed of atoms from two or more nonmetals that share pairs of electrons.

Law of Neutrality

The principle stating that all ionic compounds must be electrically neutral (overall charge of zero), meaning the positive charges of cations and negative charges of anions must balance.

Coulomb’s Law

A physical law stating that the force ($F$) between charged particles is directly proportional to their charges ($q_1$ and $q_2$) and inversely proportional to the square of the distance ($r^2$) between them: $F = k\frac{q_1 \times q_2}{r^2}$.

Law of Conservation of Mass

The principle stating that atoms are neither created nor destroyed during a chemical reaction, meaning the mass of the products must equal the mass of the reactants.

Valence Electrons

Electrons located in the outermost electron shell of an atom.

Octet Rule

The general principle that atoms want to have a total of 8 valence electrons to achieve chemical stability and drive the formation of chemical bonds.

Chemical Bond

A force that holds atoms together in a molecule or compound.

Lewis Symbol

A representation that displays valence electrons as dots placed around an element's chemical symbol.

Lewis Formula (Lewis Structure)

A representation of a molecule where atoms are shown separately, lines represent shared electron pairs (bonds), and dots represent unshared valence electrons.

Electronegativity

The ability of an atom within a molecule to attract shared electrons toward itself, which increases going up and to the right across the periodic table (excluding noble gases).

Nonpolar Covalent Bond

A covalent bond where electrons are shared equally between atoms because there is no significant difference in electronegativity.

Polar Covalent Bond

A covalent bond where electrons are shared unequally due to a difference in electronegativity, creating an uneven electron distribution.

VSEPR Model

The Valence-Shell Electron-Pair Repulsion theory, which states that electron pairs around a central atom arrange themselves to minimize repulsion, dictating the 3D geometry and bond angles of the molecule.

Electron Domain

A region of electron density around a central atom, classified either as a bonding domain (a bond to a surrounding atom) or a nonbonding domain (a lone pair on the central atom).

Electron-Domain Geometry

The three-dimensional arrangement determined by all electron domains (both bonding and nonbonding pairs) surrounding the central atom.

Molecular Geometry

The arrangement of atoms in space determined only by the bonding electron pairs around the central atom.

Intermolecular Force (IMF)

An attractive force between separate molecules (not true chemical bonds).

London Dispersion Force (LDF)

A weak intermolecular attraction caused by temporary induced dipoles that occurs in every molecule, increasing in strength with greater molecular weight and greater molecular surface area.

Dipole-Dipole Force

An intermolecular attraction occurring between polar molecules with permanent dipoles, where the partially positive end of one molecule attracts the partially negative end of another.

Hydrogen Bonding Force

A strong dipole-dipole attraction that occurs when a hydrogen atom covalently bonded to nitrogen ($N$), oxygen ($O$), or fluorine ($F$) is attracted to an $N$, $O$, or $F$ atom of another molecule.

Electrolyte

A compound that releases ions when dissolved in water, allowing the solution to conduct electricity (typical of ionic compounds).

Nonelectrolyte

A compound that does not release ions when dissolved in water, keeping its molecules intact in solution (typical of molecular/covalent compounds).