Holt McDougal Chemistry Chapter 6

Chemical Bond

Chemical Bond

Mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the nuclei together.

Chemical Bonds

Do most atoms exist as independent particles, or as part of chemical bonds?

Minimize

Nature favors arrangements that _________ potential energy.

Cations

Main-group elements tend to form ________.

Anions

Nonmetals tend to form ________.

Ionic Bonding

Chemical bonding that results from the electrical attraction between cations and anions. Electrons are transferred.

Covalent Bonding

Chemical bonding that results from the sharing of electron pairs between two atoms.

Electronegativity

What elemental property is used to calculate the degree to which bonding between atoms of two elements is ionic or covalent?

1.7

Below what electronegativity difference typically indicates a covalent compound?

Covalent

Bonding between two atoms of the same element is completely _________.

Nonpolar Covalent Bond

A covalent bond in which the bonding electrons are shared equally by the bonded atoms, resulting in a balanced distribution of electrical charge.

0.3

Below what electronegativity difference typically indicates a nonpolar covalent compound?

Polar Bond

Chemical bond with an uneven distribution of charge.

Polar Covalent Bond

Covalent bond in which the bonded atoms have an unequal attraction for the shared electrons.

0.3 and 1.7

Between what electronegativity differences typically indicate a polar covalent compound?

1.7

Above what electronegativity difference typically indicates an ionic compound?

Molecule

A neutral group of atoms that are held together by covalent bonds. Capable of existing on its own

Molecular Compound

A chemical compound whose simplest units are molecules.

Chemical Formula

Indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts.

Molecular Formula

Shows the types and numbers of atoms combined in a single molecule of a molecular compound. The chemical formula of a molecular compound.

Diatomic Molecule

Molecule that contains only two atoms.

Potential Energy

Nature favors chemical bonding because most atoms have lower ________ ________ when they are bonded to other atoms than when they are independent particles.

Bond Length

The distance between two bonded atoms at their minimum potential energy

Bond Energy

The energy required to break a chemical bond and form neutral isolated atoms.

Noble Gases

What atoms exist independently in nature?

Octet Rule

Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest-occupied energy level.

Expanded Valence

Case in which bonding involves electrons in d orbitals, as well as in s and p orbitals. Usually happens when elements bond with highly electronegative elements, such as oxygen, fluorine, and chlorine.

Electron Dot Notation

An electron configuration notation in which only the valence electrons of an atom of a particular element are shown, indicated by dots placed around the element’s symbol.

Unshared/Lone Pair

A pair of electrons that is not involved in bonding and that belongs exclusively to one atom.

Lewis Structures

Formulas in which atomic symbols represent nuclei and inner-shell electrons, dot-pairs or dashes between two atomic symbols represent electron pairs in covalent bonds, and dots adjacent to only one atomic symbol represent unshared electrons

Structural Formula

Indicates the kind, number, arrangement, and bonds, but not the unshared pairs, of the atoms in a molecule.

Single Bond

Covalent bond in which one pair of electrons is shared between two atoms.

Double Bond

Covalent bond in which two pairs of electrons are shared between two atoms.

Triple Bond

Covalent bond in which three pairs of electrons are shared between two atoms.

Multiple Bonds

Double and triple bonds.

Stronger; Shorter

Double bonds are typically _________ and _________ than single bonds. Triple bonds even more so.

Resonance

Refers to bonding in molecules or ions that cannot be correctly represented by a single Lewis structure.

Resonance Structures

Different structures for molecules that are averaged to form one structure.

Continuous

There are many covalently-bonded compounds that do not contain individual molecules; they are instead pictured as ___________, three-dimensional networks of bonded atoms.

Ionic Compound

Composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal. Most exist as crystalline solids.

Ionic Crystal

Three-dimensional network of positive and negative ions that are mutually attracted to each other.

Formula Unit

The simplest collection of atoms from which an ionic compound’s formula can be written.

Okay

Ionic compounds are not composed of independent, neutral units that can be isolated and examined, unlike molecular compounds. In addition, they do not ordinarily form from the combination of isolated ions.

Crystal Lattice

Orderly arrangement in which ions in an ionic crystal minimize their potential energy by combining in this way.

Lattice Energy

The energy released when one mole of an ionic crystalline compound is formed from gaseous ions.

Weaker

The forces of attraction between molecules are ________ than the forces of among formula units in ionic bonding.

Ionic

Do molecular or ionic compounds have higher melting and boiling points?

Ionic

Are molecular or ionic compounds hard and brittle?

Liquid (Molten)

In what state do ionic compounds have to be in in order to carry electric current?

Polyatomic Ion

A charged group of covalently bonded atoms. The charge results from either an excess or a shortage of electrons. They combine with ions of opposite charge to form ionic compounds.

Valence Electrons

Metals in the solid state are excellent conductors of electricity, much better than molten ionic compounds, because of their highly mobile _________ _____________.

Overlap

Within a metal, the vacant orbitals in the atoms’ outer energy levels _________. This allows the outer electrons to roam freely throughout the entire metal.

Delocalized

Refers to electrons that do not belong to any one atom, but move freely about the metal’s network of empty atomic orbitals.

Sea of Electrons

Mobile electrons packed together in a crystal lattice formed around metals atoms.

Metallic Bonding

The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons.

Light

Metals are strong absorbers and reflectors of ________.

Reradiation of Light

What gives metals their characteristic luster?

Malleability

The ability of a substance to be hammered or beaten into thin sheets.

Ductility

The ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire.

Same

Metallic bonding is the _______ in all directions throughout the solid. This is why the malleability and ductility of metals are possible.

Enthalpy of Vaporization

The amount of energy absorbed as heat when a specified amount of a substance vaporizes at constant pressure. The amount of energy as heat required to vaporize a metal is a measure of the strength of the bonds that hold the metal together.

Molecular Geometry

The three-dimensional arrangement of a molecule’s atoms in space.

Molecular Polarity

The uneven distribution of molecular charge.

VSEPR Theory

States that repulsion between the sets of valence-level electrons surrounding an atom causes these sets to be oriented as far apart as possible.

Far Apart

Atoms bonded to the central atom in a molecule will be as _________ __________ as possible in a three-dimensional space.

Atoms

Lone pairs occupy space, but the description of the observed shape of a molecule refers to the positions of _______ only.

Hybridization

The mixing of two or more atomic orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal energies.

SP^3

Example of a hybrid orbital. The 1 superscript on the s is understood, and the 3 superscript indicates that three p orbitals were included in the hybridization. Four of these can be produced, as four orbitals are involved in the hybridization.

Hybrid Orbitals

Orbitals of equal energy produced by the combination of two or more orbitals on the same atom.

Boiling Point

________ ________ is a good measure of the force of attraction between particles of a liquid.

Kinetic Energy

As a liquid is heated, the _________ ________ of its particles increases.

Intermolecular Forces

The forces of attraction between molecules. Generally weaker than bonds between atoms.

Polar Molecules

Between what molecules are the strongest intermolecular forces?

Dipole

Created by equal, but opposite charges that are separated by a short distance. The negative end will probably be at the more electronegative element.

Dipole-Dipole Forces

The forces of attraction between polar molecules. They are short-range, acting only between nearby molecules.

Dipole; Nonpolar; Electrons

A polar molecule can temporarily induce a ______ in a _______ molecule by attracting its ________.

Hydrogen Bonding

The intermolecular force in which a hydrogen atom that is bonded to a highly electronegative atom is attracted to un unshared pair of electrons of an electronegative atom in a nearby molecule.

London Dispersion Forces

The intermolecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles. The only intermolecular forces acting among noble-gas atoms and nonpolar molecules.