Pre-AP Chemistry Exam Review

A comprehensive set of vocabulary flashcards based on the Pre-AP Chemistry exam transcript covering atomic structure, periodic trends, bonding, and thermal chemistry.

Metalloid

An element that has properties of both metals and nonmetals, such as silicon ($Si$), germanium ($Ge$), or arsenic ($As$).

Isotopes

Nuclides of the same element that have the same number of protons but different numbers of neutrons (e.g., $I-131$ and $I-133$).

Electrically Neutral

An atom is considered this when its number of protons equals its number of electrons.

Orbital

A region around the nucleus where an electron is likely to be found, according to the modern wave-mechanical model.

Atomic Number

The number of protons in an atom, which remains the same for all atoms of a specific element (e.g., uranium).

Excited State

An electron configuration where electrons have moved to higher energy levels without filling lower ones first (e.g., potassium configuration $2-8-7-2$).

Valence Electrons

The electrons located in the outermost energy level of an atom that determine its chemical properties and bonding behavior.

Octet

A stable electron configuration consisting of 8 valence electrons.

Halogens

The group of elements found in Group 17 of the Periodic Table.

Noble Gas

A non-reactive element found in Group 18 of the Periodic Table, such as krypton ($Kr$).

Electronegativity

A measure of an atom's attraction for shared electrons within a chemical bond.

Cation

A positively charged ion formed when a metal atom loses one or more electrons and shrinks in size.

Physical Change

A change that affects the physical properties or state of a material (like melting chocolate or ice) without altering its chemical composition.

Chemical Change

A change where the chemical composition of a substance is altered and a new substance is formed.

Endothermic

A chemical reaction or process that absorbs heat energy from its surroundings.

Exothermic

A chemical reaction or process that releases heat energy into its surroundings.

Entropy

A measure of the disorder or randomness of a system, which is greatest in the gas phase.

Sublimation

The phase change where a substance changes directly from a solid to a gas, such as dry ice ($CO_2(s)$) becoming vapor.

Allotropes

Different structural modifications of the same element (e.g., diamond and graphite for carbon) that have different physical properties.

Molecular Formula

A chemical formula that shows the true, unreduced composition of a known substance, such as $C_2H_6$.

Empirical Formula

A chemical formula that shows the simplest or smallest whole-number ratio of atoms in a substance, such as reducing $C_2H_6$ to $CH_3$.

Qualitative Information

Information in a chemical formula that describes the specific types of atoms or ions present.

Quantitative Information

Information in a chemical formula that describes the exact number of each atom present.

Subscript

A small whole number written to the bottom right of an element's symbol indicating the number of atoms of that element in a formula.

Ionic Bond

A bond formed by the complete transfer of electrons from a metal to a nonmetal, creating oppositely charged particles.

Covalent Bond

A bond formed when two nonmetal atoms share electrons.

Polar Covalent Bond

A covalent bond where electrons are shared unequally due to a difference in electronegativity, such as in $HCl$.

Malleability

The ability of a metal to be hammered or flattened into thin sheets without shattering.

Ductility

The ability of a metal to be drawn into thin wires without shattering.

Kinetic Molecular Theory (KMT)

A model describing gas behavior where energy is transferred between colliding particles but total energy is conserved.

Standard Temperature and Pressure (STP)

Baseline metrics defined as $101.3\,kPa$ and $0\,^{\circ}\text{C}$ (or $273\,K$).

Gram-formula mass (GFM)

The sum of the atomic masses of all atoms in a formula, such as $40\,g/mol$ for $NaOH$.

Homogeneous Mixture

A mixture, such as an aqueous solution, where particles are distributed uniformly throughout.

Heat of Fusion ($H_f$)

The amount of heat energy released or absorbed during a change between the solid and liquid phases.