Atoms, Molecules, and Ions Vocabulary Flashcards

Vocabulary flashcards covering key terms, definitions, subatomic properties, periodic classifications, chemical formulas, and physical properties from Chapter 2 lecture notes.

Atom

The smallest unit of an element that has all the properties of that element.

Law of Constant Composition

The principle stating that all samples of a pure substance contain the same elements in the same proportion by mass.

Law of Multiple Proportions

The principle stating that when the same elements form more than one compound, the mass of one element that combines with a fixed mass of a second element are in a ratio of small whole numbers.

Law of Conservation of Mass

The principle stating that there is no detectable change in mass when a chemical reaction occurs.

Electron

A negatively charged subatomic particle with a charge of $-1.602 \times 10^{-19}\,\text{coulombs}$ and a mass of $9.109 \times 10^{-31}\,\text{kg}$.

Proton

A positively charged subatomic particle present in the nucleus with a charge equal in magnitude to the electron ($+1.602 \times 10^{-19}\,\text{coulombs}$) and a mass of $1.673 \times 10^{-27}\,\text{kg}$.

Neutron

A neutral subatomic particle present in the nucleus with a charge of $0$ and a mass of $1.675 \times 10^{-27}\,\text{kg}$, which is almost the same as that of a proton.

Atomic Number ($Z$)

The number of protons in the nucleus of an atom.

Mass Number ($A$)

The sum of the numbers of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of an element whose nuclei contain different numbers of neutrons (same atomic number $Z$, different mass number $A$).

Cation

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

Anion

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

Atomic Mass Unit ($u$)

A relative mass unit defined as $\frac{1}{12}$ of the mass of one $^{12}\text{C}$ atom, where $1\,u = 1.66 \times 10^{-27}\,\text{kg}$.

Isotopic Mass

The mass, in atomic mass units ($u$), of a particular isotope of an element.

Atomic Mass

The weighted average mass of the naturally occurring isotopes of an element.

Periodic Table

An arrangement of elements placing those with similar properties in the same column, proposed independently by Dimitri Mendeleev and Lothar Meyer.

Period

A horizontal row on the periodic table.

Group

A vertical column on the periodic table containing chemically similar elements; also known as a family.

Metal

An element that is shiny and a good electrical conductor, located on the center and left side of the periodic table.

Nonmetal

An element that is typically a nonconductor, located in the top right of the periodic table.

Metalloid

An element that has properties of both metals and nonmetals, found on the staircase separating metals and nonmetals on the periodic table.

Representative Elements

The elements in the A groups (1A–8A or groups 1, 2, 13–18) of the periodic table.

Transition Metals

The elements in the B groups (1B–8B or groups 3–12) of the periodic table.

Inner Transition Metals

The two rows of metals, consisting of lanthanides and actinides, set at the bottom of the periodic table.

Alkali Metals

Soft, reactive metals located in group 1A (1) of the periodic table.

Alkaline Earth Metals

Elements located in group 2A (2) of the periodic table.

Halogens

Reactive nonmetals in group 7A (17) of the periodic table, also known as salt-formers.

Noble Gases

Stable, largely inert gases located in group 8A (18) of the periodic table.

Molecule

A combination of atoms joined so strongly that they behave as a single particle.

Homonuclear Diatomics

Diatomic molecules containing two of the same atom, such as nitrogen gas ($\text{N}_2$).

Heteronuclear Diatomics

Diatomic molecules containing two different atoms, such as nitrogen monoxide ($\text{NO}$).

Molecular Compound

A compound formed when two or more elements form a molecule, typically composed of nonmetals.

Molecular Formula

A chemical formula that gives the exact number of every type of atom in a molecule.

Structural Formula

A representation showing how the atoms are connected within a molecule.

Molecular Mass

The sum of the atomic masses of all atoms present in the molecular formula of a compound, expressed in atomic mass units ($u$).

Ionic Compound

A neutral species composed of cations and anions, generally formed by combining metals with nonmetals.

Polyatomic Ion

A group of atoms with a net charge that behaves as a single particle.

Formula Mass

The sum of the atomic masses of all the atoms in the empirical formula of an ionic compound.

Acid

A compound that produces hydrogen cations when dissolved in water.

Hydrocarbons

Organic compounds that contain only the elements hydrogen and carbon.

Alkanes

Hydrocarbons that have the general formula $\text{C}_n\text{H}_{2n+2}$, where $n$ is an integer.

Cycloalkanes

Hydrocarbons containing a ring of carbon atoms with the general formula $\text{C}_n\text{H}_{2n}$.

Alkyl Group

An alkane substituent created by removing one hydrogen atom from the chain, named with a "-yl" ending.

Electrolyte

A substance that forms ions in water solution and conducts electricity.

Nonelectrolyte

A substance that dissolves in water as neutral molecules and does not conduct electrical current.