Chapter 3 Chemical Compounds

Polyatomic ion

A charged collection of atoms held together by covalent bonds.

Molecular compound

A compound composed of molecules. In such compounds, all of the bonds between atoms are covalent bonds.

Ionic Compound

A compound that consists of ions held together by ionic bonds.

Binary covalent compound

A compound that consists of two nonmetallic elements.

Chemical formula

A concise written description of the components of a chemical compound. It identifies the elements in the compound by their symbols and indicates the relative number of atoms of each element with subscripts.

Polar covalent bond

A covalent bond in which electrons are shared unequally, leading to a partial negative charge on the atom that attracts the electrons more and to a partial positive charge on the other atom.

Nonpolar covalent bond

A covalent bond in which the difference in electron-attracting ability of two atoms in a bond is negligible (or zero), so the atoms in the bond have no significant charges.

Double bond

A link between atoms that results from the sharing of four electrons. It can be viewed as two 2 electron covalent bonds.

Triple bond

A link between atoms that results from the sharing of six electrons. It can be viewed as three 2 electron covalent bonds.

Lewis structure

A representation of a molecule that consists of the elemental symbol for each atom in the molecule, lines to show covalent bonds, and pairs of dots to indicate lone pairs.

Electron-dot symbol

A representation of an atom that consists of its elemental symbol surrounded by dots representing its valence electrons.

Mixture

A sample of matter that contains two or more pure substances and has variable composition.

Pure substance

A sample of matter that has constant composition. There are two types of pure substances, elements and compounds.

Compound

A substance that contains two or more elements, the atoms of these elements always combining in the same whole-number ratio.

Chemical bond

An attraction between atoms or ions in chemical compounds. Covalent bonds and ionic bonds are examples.

Binary ionic compound

An ionic compound whose formula contains one symbol for a metal and one symbol for a nonmetal

Monatomic anions

Negatively charged particles, such as Cl-, O2-, and N3-, that contain single atoms with a negative charge.

Monatomic cations

Positively charged particles, such as Na+, Ca2+, and Al3+, that contain single atoms with a positive charge.

Lone pair

Two electrons that are not involved in the covalent bonds between atoms but are important for explaining the arrangement of atoms in molecules. They are represented by pairs of dots in Lewis structures.

Alcohols

Compounds that contain a hydrocarbon group with one or more -OH groups attached.

Hydrocarbons

Compounds that contain only carbon and hydrogen.

Bond angle

The angle formed by straight lines (representing bonds) connecting the nuclei of three adjacent atoms.

Ionic bond

The attraction between a cation and an anion.

Organic chemistry

The branch of chemistry that involves the study of carbon-based compounds.

Valence electrons

The electrons that are most important in the formation of chemical bonds. The number of valence electrons for the atoms of an element is equal to the element's A-group number on the periodic table. (A more comprehensive definition of valence electrons appears in Chapter 12.)

Tetrahedral

The molecular shape that keeps the negative charge of four electron groups as far apart as possible. This shape has angles of 109.5° between the atoms.