Lecture Notes Review: Atoms, Ions, Equations, and Reactions (VOCABULARY)

Vocabulary flashcards covering atoms, elements, molecules, ions, and common reaction types and tests from the notes.

Atom

The smallest part of an element that has the properties of that element.

Element

A pure substance that cannot be split into anything simpler and contains atoms of only one type.

Molecule

A group of two or more atoms bonded together; in elements, a molecule contains atoms of the same element (e.g., H2, O2, N2, Cl2); in compounds, it contains atoms of different elements in a fixed ratio (e.g., H2O, CO2).

Diatomic element

A type of element that naturally exists as two bonded atoms (examples include N2, O2, Cl2).

Molecule of an element

A molecule composed of atoms of the same element (diatomic or more), such as H2 or O2.

Compound

A substance that contains atoms of different elements chemically bonded in a fixed ratio.

Fixed ratio

The definite proportion in which elements combine to form compounds.

Ion

A species consisting of one or more atoms that has a positive or negative charge.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Monoatomic element

An element that is made up of single atoms (e.g., He, Ne).

Polyatomic (group)

A molecule made up of several atoms joined together (e.g., H2O, CO2).

Ionic equation

An equation that shows the ions present in an aqueous solution and their reactions.

Precipitation reaction

A reaction in which an insoluble solid (precipitate) forms from soluble reactants.

Displacement reaction

A reaction in which a more reactive element replaces a less reactive element in a compound.

Redox (oxidation-reduction) reaction

A reaction involving transfer of electrons; oxidation is loss of electrons, reduction is gain of electrons.

Oxidation

Loss of electrons by a species in a chemical reaction.

Reduction

Gain of electrons by a species in a chemical reaction.

Acid

A substance that donates H+ ions (proton donor) in aqueous solutions.

Proton donor

Another way to say an acid in the Brønsted–Lowry sense.

Acid with metals

Acids react with metals to produce a salt and hydrogen gas.

Metal oxide + acid → salt + water

Acids react with metal oxides to form a salt and water.

Metal hydroxide + acid → salt + water

Acids react with metal hydroxides to form a salt and water.

Acids with carbonates (and hydrogen carbonates)

Acids react with carbonates to give a salt, carbon dioxide, and water (and similarly with hydrogen carbonates).

Carbon dioxide test (limewater test)

Passing CO2 through limewater turns it milky due to formation of calcium carbonate.

Sulfate test

Addition of Ba2+ (e.g., BaCl2 or Ba(NO3)2) forms a white precipitate of BaSO4 if sulfate ions are present.

Halide test

Addition of Ag+ from AgNO3 forms insoluble silver halide precipitates (AgCl, AgBr, AgI) for chloride, bromide, and iodide ions.

Lead(II) nitrate + potassium iodide reaction

Pb(NO3)2 + 2 KI → PbI2(s) + 2 KNO3, a precipitation reaction showing formation of lead(II) iodide.