CH 2: Atoms, Molecules, and Ions Vocabulary

Vocabulary flashcards covering core concepts of atomic structure, subatomic particles, isotopes, chemical formulas, periodic table organization, and chemical bonding from Chapter 2.

Nucleus

The small, dense core at the center of an atom that contains protons and neutrons.

Proton

A positively charged subatomic particle located in the nucleus with a mass of $1.6726 \times 10^{-24}\,\text{g}$ ($1.0073\,\text{amu}$) and a relative charge of $+1$.

Neutron

A neutral subatomic particle located in the nucleus with a mass of $1.6749 \times 10^{-24}\,\text{g}$ ($1.0087\,\text{amu}$) and a relative charge of $0$.

Electron

A low-mass, negatively charged subatomic particle located outside the nucleus with a mass of $0.0009 \times 10^{-24}\,\text{g}$ ($0.0006\,\text{amu}$) and a relative charge of $-1$.

Atomic number ($Z$)

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

Mass number ($A$)

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

Isotopes

Atoms of the same element that have the same number of protons but a different number of neutrons, resulting in different masses.

Atomic mass

The average mass of the isotopes that compose an element, weighted according to the natural abundance of each isotope.

Atomic elements

Elements that exist in nature with single atoms as their basic units, such as helium ($\text{He}$) or carbon ($\text{C}$).

Molecular elements

Elements that exist in nature as molecules composed of two or more atoms of the same element bonded together, such as $\text{O}_2$ or $\text{S}_8$.

Diatomic molecular elements

Seven elements whose basic unit is a two-atom molecule: $\text{H}_2$, $\text{N}_2$, $\text{O}_2$, $\text{F}_2$, $\text{Cl}_2$, $\text{Br}_2$, and $\text{I}_2$.

Empirical formula

A chemical formula that gives the relative number of atoms of each element in a compound as the smallest whole-number ratio.

Molecular formula

A chemical formula that gives the actual number of atoms of each element in a molecule of a compound.

Structural formula

A formula that uses lines to represent chemical bonds and shows how the atoms in a molecule are connected to one another.

Periodic Law

The principle stating that the chemical and physical properties of elements are periodic functions of their atomic numbers.

Periods (Series)

The horizontal rows of elements in the periodic table.

Groups (Families)

The vertical columns of elements in the periodic table that group together elements with similar chemical properties.

Metals

Elements that are typically shiny, ductile, malleable, and good conductors of heat and electricity.

Nonmetals

Elements that appear dull and are poor conductors of heat and electricity.

Metalloids

Elements that conduct heat and electricity moderately well and possess properties intermediate between metals and nonmetals.

Cation

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

Anion

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

Ionic bond

A chemical bond formed by the electrostatic attraction between cations and anions following the transfer of electrons from a metal to a nonmetal.

Covalent bond

A chemical bond formed when two nonmetals share electrons.

Molecular compounds

Compounds composed of two or more covalently bonded nonmetals, whose basic structural units are molecules.

Ionic compounds

Compounds composed of cations (metals) and anions (nonmetals) bound together by ionic bonds.

Formula unit

The smallest, neutral collection of ions that serves as the basic structural unit of an ionic compound.

Polyatomic ion

An ion composed of two or more covalently bonded atoms carrying a net positive or negative charge.