Chemistry: Particle Model, Matter, and the Periodic Table

Vocabulary practice flashcards covering states of matter, particle theory, atomic structure, classification of substances, chemical formulas, and periodic table trends.

Particle Model of Matter

A scientific model stating that a sample of a substance is a collection of tiny, identical particles with forces of attraction holding them together and kinetic energy keeping them constantly moving.

Kinetic Energy (Particle Model)

The energy of motion possessed by particles; heating a substance increases this energy causing particles to move faster, while cooling removes energy causing them to move more slowly.

Thermal Expansion

The increase in volume of a sample of a substance when heated, caused by particles gaining energy, moving faster, and pushing further apart.

Elemental Substance

A substance composed entirely of the same type of atom, existing either as isolated single atoms or as molecules of two or more identical atoms joined together (e.g., $O_2$, $H_2$).

Compound Substance

A substance made up of two or more different types of atoms chemically combined in fixed ratios (e.g., $H_2O$, $C_6H_{12}O_6$, $NaCl$).

Mixture

A combination of different substances that are mixed together physically rather than chemically combined, having no fixed ratios (e.g., air, salt water, vinegar).

Heterogeneous Mixture

A mixture that exists in two or more distinct phases where the separate parts can be easily seen, such as oil and water or a rock.

Homogeneous Mixture

A mixture uniform in composition that presents as a single blended mix looking identical throughout, such as air or a salt solution.

Reactants

The starting substances present before a chemical reaction occurs, written on the left side of a chemical equation.

Products

The new substances formed as a result of a chemical reaction, written on the right side of a chemical equation.

Conservation of Mass in a Gas-Producing Reaction

The principle that mass is conserved in a reaction; when hydrochloric acid and sodium hydrogen carbonate react in an open flask, the balance reading decreases because carbon dioxide gas escapes, whereas in a sealed balloon system, the total mass remains unchanged.

Group 17 (The Halogens)

Elements with seven valence electrons (one missing from their outer shell) whose nuclei have a strong pull on electrons; they react by gaining one electron, and their reactivity decreases down the group with fluorine being the most reactive.

Halide Ion

An ion formed when a halogen atom gains one electron to complete its valence shell, resulting in an electric charge of $-1$.

Group 18 (The Noble Gases)

Chemically unreactive, stable monoatomic gases (He, Ne, Ar, Kr, Xe, Rn) that possess completely filled outer shells of electrons and rarely lose or gain electrons.

Cation

A positively charged ion formed when a neutral atom loses one or more electrons, resulting in fewer electrons than protons (e.g., $Na^+$).

Anion

A negatively charged ion formed when a neutral atom gains one or more electrons, resulting in more electrons than protons (e.g., $Cl^-$).

Isotopes

Atoms of the same chemical element that have the identical number of protons (same atomic number) but different numbers of neutrons (different mass numbers).

Nuclear Symbol Notation ($^A_Z X^Q$)

The standard representation of an atom or ion where $X$ is the element symbol, $A$ is the mass number, $Z$ is the atomic number, and $Q$ is the net electrical charge.

Atomic Number ($Z$)

The total number of protons located within the nucleus of an atom, which uniquely determines the element's identity and position on the periodic table.

Mass Number ($A$)

The total count of nucleons (protons plus neutrons) found in the nucleus of an atom, calculated as $A = Z + N$.

Group (Periodic Table)

A vertical column of elements in the periodic table containing elements whose atoms share the same number of outer-shell (valence) electrons and exhibit similar chemical properties.

Period (Periodic Table)

A horizontal row of elements in the periodic table containing elements whose atoms have the same number of occupied electron shells.

Natrium

The Latin origin of sodium's chemical symbol ($Na$), derived from the Greek 'nitron' or Arabic 'natrun' referring to sodium carbonate.

Kalium

The Latin origin of potassium's chemical symbol ($K$), derived from the Arabic 'al qalwy' meaning calcined ashes.

Wolfram

The German origin of tungsten's chemical symbol ($W$), named after the mineral wolframite ('wolf rahm' or 'wolf's foam') because of the tin eaten during smelting.

Hydrargyrum

The Latin origin of mercury's chemical symbol ($Hg$), derived from the Greek 'hydrargyros' meaning liquid silver (formerly referred to in English as quicksilver).

Plumbum

The Latin origin of lead's chemical symbol ($Pb$), which is also the historical linguistic root of the English words 'plumbing' and 'plumber' due to lead's use in water pipes.

Physical Properties of Metals

Typical characteristics of solid metallic elements, including good electrical conductivity, good thermal conductivity, shiny appearance, high density, malleability, and ductility.

Physical Properties of Non-metals

Typical characteristics of solid non-metallic elements, including poor electrical conductivity, poor heat conductivity, dull appearance, lower density, and brittleness.

Chemical Formula Subscripts

Numbers written to the lower right of an element's symbol in a formula that specify the exact number of atoms of that element present in the particle (e.g., the 2 and 4 in $Na_2SO_4$).

Formula Brackets

Notation used to show that a group of atoms acts as a single compound unit (such as $(OH)$ in $Ca(OH)_2$), where every atom inside the bracket is multiplied by the following subscript.

Group 2 Reactivity Trend

The trend in alkaline earth metals where reactivity increases down the group; for example, calcium reacts vigorously with water and violently with acid with high heat release, whereas magnesium reacts far more slowly with water.

Bohr Model

An atomic model proposed by Niels Bohr in the 1920s depicting an atom with a central nucleus composed of protons and neutrons surrounded by electrons orbiting in defined electron shells.

First Electron Shell Capacity

The electron capacity rule established in Bohr models specifying that the innermost orbit closest to the nucleus can hold a maximum of 2 electrons.

Group 1 (The Alkali Metals)

A family of soft, low-density, low-melting-point metals with 1 outer shell electron that react exothermically with water to produce hydrogen gas and alkaline metal hydroxide solutions.

Alkali Metal Reactivity Trend

A periodic trend in Group 1 showing that elements become progressively more reactive as you move down the column from lithium to caesium.

Alkali Metal Melting Point Trend

A physical trend in Group 1 where melting points decrease steadily down the group, dropping from $180^\text{o}\text{C}$ in lithium ($Li$) down to $28^\text{o}\text{C}$ in caesium ($Cs$).