Atoms, Molecules, and Ions Vocabulary Flashcards

Flashcards containing key terms and definitions covering atomic structure, subatomic particles, isotopes, periodic table groups, chemical formulas, and mole concept topics.

Atom

The smallest building block of matter, containing a small nucleus composed of positively charged protons and uncharged neutrons, surrounded by space containing negatively charged electrons.

Proton

A subatomic particle located in the nucleus with a unit charge of $+1$ and a mass of $1.00727\,amu$.

Neutron

A subatomic particle located in the nucleus with a unit charge of $0$ and a mass of $1.00866\,amu$.

Electron

A subatomic particle located outside the nucleus with a unit charge of $-1$ and a mass of $0.00055\,amu$.

Fundamental unit of charge ($e$)

The magnitude of electric charge, where $e = 1.602 \times 10^{-19}\,C$.

Atomic mass unit (amu)

A standard unit of mass defined such that $1\,amu = 1.66 \times 10^{-24}\,g$, which is equal to $\frac{1}{12}$ of the mass of one $^{12}\text{C}$ atom.

Atomic number ($Z$)

The number of protons contained in the nucleus of an atom.

Mass number ($A$)

The total number of protons plus neutrons in an atom.

Anions

Negatively charged atoms formed when an atom gains one or more electrons.

Cations

Positively charged atoms formed when an atom loses one or more electrons.

Isotopes

Atoms of the same element with the same atomic number $Z$ but different mass number $A$ due to a different number of neutrons.

Periods

Horizontal rows on the periodic table in which elements are arranged in order of increasing atomic number.

Group

A vertical column of elements in the periodic table.

Main group elements

The elements located in Groups 1A through 7A of the periodic table.

Transition metals

The elements located in Groups 3B-8B and 1B of the periodic table.

Alkali metals

The elements belonging to Group 1A of the periodic table.

Alkaline earth metals

The elements belonging to Group 2A of the periodic table.

Pnictogens

The Group 5A elements in the periodic table, which include $\text{N}$, $\text{P}$, $\text{As}$, $\text{Sb}$, and $\text{Bi}$.

Chalcogens

The Group 6A elements in the periodic table, which include $\text{O}$, $\text{S}$, $\text{Se}$, $\text{Te}$, and $\text{Po}$.

Halogens

The elements belonging to Group 7A of the periodic table.

Noble gases

The elements belonging to Group 8A of the periodic table.

Element

A pure substance that is composed of atoms of the same type.

Compound

A substance composed of two or more different types of atoms combined in a specific ratio and held together by chemical bonds.

Molecule

A combination of two or more atoms in a specific arrangement held together by chemical bonds.

Molecular formula

A representation of a molecule that uses chemical symbols to indicate the types of atoms followed by subscripts to show the actual number of atoms of each type in the molecule.

Structural formula

A representation for a compound that shows how the atoms are connected in the molecule in addition to indicating the types and numbers of atoms present.

Empirical formula

A chemical formula that indicates the types of atoms present and the simplest whole-number ratio of the number of atoms (or ions) in the compound.

Chemical bond

An attraction between atoms or ions that holds them together in a molecule or a crystal.

Avogadro's number ($N_A$)

The constant $6.02214179 \times 10^{23}$, representing the number of $^{12}\text{C}$ atoms in $12\,g$ of pure carbon-12.

Mole

An amount unit defined as the amount of substance containing $6.022 \times 10^{23}$ discrete entities (such as atoms, molecules, or ions).

Molar mass

The mass in grams of $1\,mol$ of a given substance, expressed in units of grams per mole ($g/mol$).