Chapter 2: Atoms, Ions and Molecules

A complete set of vocabulary flashcards covering basic atomic structure, subatomic particles, radioactive decay emissions, atomic mass, isotopes, periodic table organization, chemical formulas, and fundamental organic chemistry concepts.

Electron

A subatomic particle that has a negative charge and essentially zero mass, located in the empty space surrounding the nucleus.

Proton

A positively charged subatomic particle present in the nucleus of an atom, with a mass of $1.67262 \times 10^{-24}\,\text{g}$ ($1.00727\,\text{amu}$).

Neutron

A neutral subatomic particle present in the nucleus of an atom, with a mass of $1.67493 \times 10^{-24}\,\text{g}$ ($1.00866\,\text{amu}$).

Cathode Rays

A stream of electrons emitted by the cathode in a partially evacuated tube.

Millikan Oil Drop Experiment

An experiment conducted by R. Millikan that determined the electric charge of an electron.

Radioactivity

The spontaneous emission of high-energy radiation and particles by unstable materials.

Beta ($\beta$) Particle

A radioactive emission that consists of a high-energy electron.

Alpha ($\alpha$) Particle

A radioactive emission that consists of a high-energy helium nucleus.

Gold Foil Experiment

The Rutherford-Geiger-Marsden experiment in which alpha particles were directed at thin gold foil to establish the nuclear model of atomic structure.

Atomic Mass Unit (amu)

A unit used to express the relative mass of atoms and subatomic particles, defined as exactly $\frac{1}{12}$ of the mass of a carbon atom.

Dalton (Da)

A unit of mass identical to $1\,\text{amu}$, most often used in biology.

Isotopes

Atoms of an element containing different numbers of neutrons while maintaining the same number of protons.

Nuclide Symbol

A notation of the form $_Z^AX$ specifying the subatomic makeup of an atomic nucleus, where $Z$ is atomic number, $A$ is mass number, and $X$ is element symbol.

Atomic Number ($Z$)

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

Mass Number ($A$)

The total number of nucleons (protons and neutrons) in an atomic nucleus.

Ion

An atom or group of atoms that has a net positive or negative charge.

Isoelectronic

Having the exact same number and structure of electrons.

Average Atomic Mass

A weighted average of the masses of all naturally occurring isotopes of an element, calculated by multiplying each isotope's natural abundance by its mass in atomic mass units and summing the products.

Natural Abundance

The proportion of a particular isotope relative to all the isotopes of that element present in a natural sample.

Dmitri Mendeleev

The scientist who developed the first periodic table, organizing elements by their properties and increasing atomic mass while predicting unknown elements.

Groups (Families)

Vertical columns in the periodic table containing elements that share similar chemical and physical properties.

Periods

Horizontal rows in the periodic table containing elements with similar electronic makeups that follow a repeating pattern.

Alkali Metals

The chemical elements located in Group 1 (or IA) of the periodic table.

Alkaline Earth Metals

The chemical elements located in Group 2 (or IIA) of the periodic table.

Halogens

The chemical elements located in Group 17 (or VIIA) of the periodic table.

Noble Gases

The chemical elements located in Group 18 (or VIIIA) of the periodic table.

Main Group Elements

The representative elements located in Groups 1, 2, and 13–18 of the periodic table.

Transition Metals

The elements located in Groups 3–12 of the periodic table.

Metals

Elements on the left side of the periodic table that are typically shiny solids, good conductors of heat and electricity, malleable, and ductile.

Nonmetals

Elements with properties opposite of metals, characterized by poor thermal and electrical conductivity and brittle solid forms.

Metalloids (Semimetals)

Elements along the border between metals and nonmetals in the periodic table that possess both metal and nonmetal properties.

Law of Multiple Proportions

The principle stating that the ratio of the masses of one element that combine with a given mass of another element to form different compounds is a ratio of small, whole numbers.

Molecular Compounds

Compounds formed with covalent bonds (sharing of electrons between atoms), making discrete molecules.

Ionic Compounds

Compounds formed with ionic bonds (electrostatic interactions between positive and negative ions), typically between a metal and a nonmetal.

Empirical Formula

A chemical formula showing the lowest whole-number ratio of elements in a compound.

Formula Unit

The smallest electrically neutral unit of an ionic compound.

Organic Compounds

Molecules containing carbon atoms whose structure typically consists of carbon-carbon and carbon-hydrogen bonds, and may include heteroatoms.

Heteroatom

An atom of an element other than carbon and hydrogen within a molecule of an organic compound.

Hydrocarbon

An organic compound whose molecules are composed strictly of carbon and hydrogen atoms.

Alkane

A saturated hydrocarbon in which all carbon-carbon bonds are single bonds.

Alkene

An unsaturated hydrocarbon containing one or more carbon-carbon double bonds.

Alkyne

An unsaturated hydrocarbon containing one or more carbon-carbon triple bonds.

Functional Group

A group of atoms in the molecular structure of an organic compound that imparts characteristic chemical and physical properties.

Nucleosynthesis

The natural formation of atomic nuclei as a result of fusion and other nuclear processes.

Quarks

Elementary particles that combine to form neutrons and protons, occurring in six types: up, down, strange, charm, top, and bottom.