Chapter 2: Atoms, Molecules, and Ions Vocabulary

Vocabulary practice flashcards covering atomic theory, subatomic particles, isotopes, periodic table organization, chemical bonding, organic compounds, and nomenclature based on Chapter 2 lecture notes.

Atom

An extremely small particle of matter that retains its identity during chemical reactions.

Element

A type of matter composed of only one kind of atom, where each atom of a given kind has the same properties, such as mass.

Compound

A type of matter composed of atoms of two or more elements chemically combined in fixed proportions, such as water ($\text{H}_2\text{O}$).

Law of Conservation of Mass

A fundamental chemical law stating that the total mass remains constant during a chemical change or chemical reaction.

Law of Definite Proportion

A law formulated by Joseph Proust stating that a given compound always contains exactly the same proportion of elements by mass.

Law of Multiple Proportions

A law formulated by John Dalton stating that when two elements form a series of compounds, the ratio of the masses of the second element that combine with $1\,\text{g}$ of the first element can always be reduced to small whole numbers.

Rutherford Atomic Model

An atomic model proposed in 1911 describing an atom as having a small, extremely dense center of positive charge (the nucleus) with electrons moving around it at a distance that is large relative to the nuclear radius.

Nucleus

The atom's central core, which is positively charged, contains protons and neutrons, and accounts for almost all of the atom's mass.

Electron

A subatomic particle found outside the nucleus that possesses a negative electrical charge and has the smallest mass among subatomic particles.

Proton

A subatomic particle found in the nucleus possessing a positive charge equal in magnitude to the electron's negative charge.

Neutron

A subatomic particle found in the nucleus that carries no electrical charge and has virtually the same mass as a proton.

Atomic Number ($Z$)

The total number of protons in the nucleus of an atom, which uniquely identifies the element.

Mass Number ($A$)

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of the same element having the same number of protons but different numbers of neutrons in their nuclei.

Periodic Table

A tabular arrangement of elements in order of increasing atomic number such that elements having similar chemical properties are positioned in vertical columns.

Periodic Law

The principle stating that similar physical and chemical properties recur periodically when elements are arranged according to increasing atomic number.

Period

A single horizontal row of elements in the periodic table.

Group

A single vertical column of elements in the periodic table; elements within the same group share similar chemical properties.

Metal

A substance that has a characteristic luster, is generally a good conductor of heat and electricity, and is malleable, ductile, and solid at room temperature (except mercury).

Nonmetal

A substance that does not exhibit metallic properties, occurring mostly as gases or hard, brittle solids (with bromine being the only liquid nonmetal).

Metalloid (Semi-metal)

An element bordering the staircase line on the periodic table that possesses both metallic and nonmetallic properties, often acting as a semiconductor.

Graphene

A form of elemental carbon consisting of a flat flake just one atom thick that displays exceptional properties and acts as a good conductor of heat and electricity.

Chemical Formula

A notation that uses atomic symbols with numerical subscripts to convey the relative proportions of atoms of different elements in a substance.

Molecule

A definite group of atoms tightly connected and chemically bonded together by attractive forces.

Molecular Formula

A chemical formula that shows the exact number of atoms of each element in the smallest unit of a substance.

Empirical Formula

A chemical formula that shows the simplest whole-number ratio of the atoms in a substance.

Valence Electrons

The electrons in an atom that participate in chemical bonding.

Ionic Bond

A chemical bond formed by the transfer of electrons between atoms.

Covalent Bond

A chemical bond formed by the sharing of electrons between atoms.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Organic Compounds

An important class of molecular substances containing carbon combined with other elements such as hydrogen, oxygen, and nitrogen.

Functional Group

A reactive portion of a molecule that undergoes predictable chemical reactions.

Hydrocarbons

Organic compounds containing only carbon and hydrogen atoms.

Polyatomic Ion

An ion consisting of two or more atoms chemically bonded together and carrying an overall electrical charge.

Chemical Equation

The symbolic representation of a chemical reaction written in terms of chemical formulas.