Chapter 8-12 Vocab

Actinides

The Period 7 elements that constitute the second inner transition series (5*f* block), which includes thorium (Th; *Z* = 90) through lawrencium (Lr; *Z* = 103)

Amphoteric

Able to act as either an acid or a base

Atomic size

A measure of how closely one atom lies next to another, determined from the distances between nuclei of adjacent atoms.

Afbau principle

The conceptual approach for building up atoms by adding one proton at a time to the nucleus and one electron to the lowest energy sublevel that is available, to obtain the ground-state electron configurations of the elements.

Covalent radius

One-half the shortest distance between nuclei of identical covalently bonded atoms.

Diamagnetism

The tendency of a species not to be attracted (or to be slightly repelled) by a magnetic field as a result of its electrons being paired

Effective nuclear charge (Zeff)

The nuclear charge an electron actually experiences as a result of shielding effects due to the presence of other electrons

Electron affinity (EA)

The energy change (in kJ) accompanying the addition of 1 mol of electrons to 1 mol of gaseous atoms or ions

Electron configuration

The distribution of electrons within the levels and sublevels of the atoms of an element; also the notation for such a distribution

Hund’s rule

A principle stating that, when orbitals of equal energy are available, the electron configuration of lowest energy has the maximum number of unpaired electrons with parallel spins

Inner electrons (core electrons)

Electrons that fill all the energy levels of an atom except the valence level; electrons also present in atoms of the previous noble gas and any completed transition series

Inner transition elements

The elements of the periodic table in which the seven inner *f* orbitals are being filled; the lanthanides and the actinides

Ionic radius

The size of an ion as measured by the distance between the nuclei of adjacent ions in a crystalline ionic compound

Ionization energy (IE)

The energy (in kJ) required for complete removal of 1 mol of electrons from 1 mol of gaseous atoms or ions

Isoelectronic

Having the same number and configuration of electrons as another species

Lanthanides (also *rare earths)*

The Period 6 (4*f*) series of inner transition elements, which includes cerium (Ce; *Z* = 58) through lutetium (Lu; *Z* = 71)

Metallis radius

One-half the shortest distance between the nuclei of adjacent individual atoms in a crystal of an element

Orbital diagram

A depiction of orbital occupancy in terms of electron number and spin shown by means of arrows in a series of small boxes or on a series of short lines

Outer electrons

Electrons that occupy the highest energy level (highest *n* value) and are, on average, farthest from the nucleus

Paramagnetism

The tendency of a species with unpaired electrons to be attracted by an external magnetic field

Pauli exclusion principle

A principle stating that no two electrons in an atom can have the same set of four quantum numbers. The principle arises from the fact that an orbital has a maximum occupancy of two electrons and their spins are paired

Penetration

The phenomenon in which an outer electron moves through the region occupied by the core electrons to spend part of its time closer to the nucleus; penetration increases the average effective nuclear charge for that electron

Periodic law

A law stating that, when the elements are arranged by atomic mass, they exhibit a periodic recurrence of properties

pseudo-noble gas configuration

The (*n* − 1) *d*10 configuration of a *p*-block metal ion that has an empty outer energy level

Shielding (screening)

The ability of other electrons, especially those occupying inner orbitals, to lessen the nuclear attraction for an outer electron

Spin quantum number (ms)

A number, either  1/2 or  -1/2 that indicates the direction of electron spin

Transition element (inner transition element)

An element that occupies the *d* block or the *f* block of the periodic table

Valence electrons

The electrons involved in compound formation; in main-group elements, the electrons in the outer level

Alloy

A mixture with metallic properties that consists of solid phases of two or more pure elements, a solid-solid solution, or distinct intermediate phases

Bond energy (also *bond enthalpy* or *bond strength*)

The standard enthalpy change (always > 0) accompanying the breakage of a given bond in 1 mol of gaseous molecules

Bond length

The distance between the nuclei of two bonded atoms

bond order

The number of electron pairs shared by two bonded atoms.

Born-Haber cycle

A series of hypothetical steps and their enthalpy changes that converts elements to an ionic compound; it is used to calculate the lattice energy.

Coulomb’s law

A law stating that the electrostatic energy between particles A and B is directly proportional to the product of their charges and inversely proportional to the distance between them:

covalent bond

A type of bond in which atoms are bonded through the sharing of electrons; the mutual attraction of the nuclei and an electron pair that holds atoms together in a molecule.

covalent bonding

The idealized bonding type that is based on localized electron-pair sharing between two atoms with little difference in their tendencies to lose or gain electrons (most commonly nonmetals).

double bond

A covalent bond that consists of two bonding pairs; two atoms sharing four electrons in the form of one σ and one π bond.

electronegativity (EN)

The relative ability of a bonded atom to attract shared electrons.

electronegativity difference ( delta EN)

The difference in electronegativities between two bonded atoms.

electron-sea model

A qualitative description of metallic bonding proposing that metal atoms pool their valence electrons in a delocalized “sea” of electrons in which the metal ions (nuclei and core electrons) are submerged in an orderly array.

infrared (IR) spectroscopy

An instrumental technique for determining the types of bonds in a covalent molecule by measuring the absorption of IR radiation.

ion pairs

A gaseous ionic molecule, formed when an ionic compound vaporizes.

ionic bonding

The idealized type of bonding based on the attraction of oppositely charged ions that arise through electron transfer between atoms with large differences in their tendencies to lose or gain electrons (typically metals and nonmetals).

lattice energy ( delta H lattice)

The enthalpy change (always positive) that accompanies the separation of 1 mol of a solid ionic compound into gaseous ions.

Lewis electon-dot symbol

A notation in which the element symbol represents the nucleus and inner electrons and surrounding dots represent the valence electrons.

lone ( unshared) pair

An electron pair that is part of an atom’s valence level but not involved in covalent bonding.

metalllic bonding

An idealized type of bonding based on the attraction between metal ions and their delocalized valence electrons.

nonpolar covalent bond

A covalent bond between identical atoms in which the bonding pair is shared equally.

octet rule

The observation that, when atoms bond, they often lose, gain, or share electrons to attain a filled outer level of eight electrons (or two for H and Li).

partial ionic character

An estimate of the actual charge separation in a bond (caused by the electronegativity difference of the bonded atoms) relative to complete separation.

polar covalent bond

A covalent bond in which the electron pair is shared unequally, so the bond has partially negative and partially positive poles.

shared (bonding) pair

An electron pair shared by two nuclei; the mutual attraction between the nuclei and the electron pair forms a covalent bond.

single bond

A bond that consists of one electron pair.

triple bond

A covalent bond that consists of three bonding pairs, two atoms sharing six electrons; one σ and two π bonds.

axial group

An atom (or group) that lies above or below the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule.

bent (V-shaped)

A molecular shape that arises when a central atom is bonded to two other atoms and has one or two lone pairs; occurs as the AX2E shape class (bond angle < 120°) in the trigonal planar arrangement and as the AX2E2 shape class (bond angle < 109.5°) in the tetrahedral arrangement.

bond angle

The angle formed by the bonds joining the nuclei of two surrounding atoms to the nucleus of the central atom, which is at the vertex.

dipole moment

A measure of molecular polarity; the magnitude of the partial charges on the ends of a molecule (in coulombs) times the distance between them (in meters).

electron deficient

Referring to a bonded atom, such as Be or B, that has fewer than eight valence electrons.

electron-pair delocalisation

The process by which electron density is spread over several atoms rather than remaining between two.

equatorial group

An atom (or group) that lies in the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule.

expanded valence shell

A valence level that can accommodate more than eight electrons by using available *d* orbitals; occurs only with central nonmetal atoms from Period 3 or higher.

formal charge

The hypothetical charge on an atom in a molecule or an ion, equal to the number of valence electrons minus the sum of all the unshared and half the shared valence electrons.

free radical

A molecular or atomic species with one or more unpaired electrons, which typically make it very reactive.

Lewis structure (formula)

A structural formula consisting of electron-dot symbols, with lines as bonding pairs and dots as lone pairs.

linear arrangment

The geometric arrangement obtained when two electron groups maximize their separation around a central atom.

linear shape

A molecular shape formed by three atoms lying in a straight line, with a bond angle of 180° (shape class AX2 or AX2E3).

molecular polarity

The overall distribution of electronic charge in a molecule, determined by its shape and bond polarities.

molecular shape

The three-dimensional arrangement of the atomic nuclei in a molecule.

octahedral arrangment

The geometric arrangement obtained when six electron groups maximize their space around a central atom; when all six groups are bonding groups, the molecular shape is octahedral (AX6; ideal bond angle = 90°).

resonance hybrid

The weighted average of the resonance structures for a species.

resonance structure (form)

One of two or more Lewis structures for a species that cannot be adequately depicted by a single structure. Resonance structures differ only in the position of bonding and lone electron pairs.

seesaw shape

A molecular shape caused by the presence of one equatorial lone pair in a trigonal bipyramidal arrangement (AX4E).

square planar shape

A molecular shape (AX4E2) caused by the presence of two lone pairs at opposite vertices in an octahedral electron-group arrangement.

T-shaped

A molecular shape caused by the presence of two equatorial lone pairs in a trigonal bipyramidal arrangement (AX3E2).

tetrahedral arrangement

The geometric arrangement formed when four electron groups maximize their separation around a central atom; when all four groups are bonding groups, the molecular shape is tetrahedral (AX4; ideal bond angle 109.5°).

trigonal bipyramidal arrangement

The geometric arrangement formed when five electron groups maximize their separation around a central atom. When all five groups are bonding groups, the molecular shape is trigonal bipyramidal (AX5; ideal bond angles, axial-center-equatorial 90° and equatorial-center-equatorial 120°).

trigonal planar arrangement

The geometric arrangement formed when three electron groups maximize their separation around a central atom. When all three groups are bonding groups, the molecular shape is trigonal planar (AX3; ideal bond angle 120°).

trigonal pyramidal arrangement

A molecular shape (AX3E) caused by the presence of one lone pair in a tetrahedral arrangement.

valence-shell electron-pair repulsion (VSEPR) theory

A model explaining that the shapes of molecules and ions result from minimizing electron-pair repulsions around a central atom.

square pyramidal shape

A molecular shape (AX5E) caused by the presence of one lone pair in an octahedral electron-group arrangement.

amorphous solid

A solid that has a poorly defined shape because its particles do not have an orderly arrangement throughout a sample.

atomic solid

A solid consisting of individual atoms held together by dispersion forces; the frozen noble gases are the only examples.

band theory

An extension of molecular orbital (MO) theory that explains many properties of metals and other solids—in particular, the differences in conductivity of metals, metalloids, and nonmetals.

body-centered cubic unit cell

A unit cell in which a particle lies at each corner and in the center of a cube.

boiling point

The temperature at which the vapor pressure inside bubbles forming in a liquid equals the external (atmospheric) pressure.

branch

A side chain appended to a polymer backbone or to the longest sequence of atoms in an organic compound.

capillarity (capillary action)

The rising of a liquid through a narrow space against the pull of gravity.

ceramic

A nonmetallic, nonpolymeric solid that is hardened by heating it to high temperatures and, in most cases, consists of silicate microcrystals suspended in a glassy cementing medium.

**Clausius-Clapeyron equation**

An equation that expresses the linear relationship between vapor pressure *P* of a liquid and temperature *T*; in two-point form, it is

condensation

The process of a gas changing into a liquid.

conduction band

In band theory, the empty, higher energy portion of the band of molecular orbitals into which electrons move when conducting heat and electricity.

conductor

A substance (usually a metal) that conducts an electric current well.

coordination number

In a crystal, the number of nearest neighbors surrounding a particle. In a complex ion, the number of ligand atoms bonded to the central metal ion.

copolymer

A polymer that consists of two or more types of monomer.

critical point

The point on a phase diagram above which the vapor cannot be condensed to a liquid; the end of the liquid-gas curve.

crosslink

A branch that covalently joins one polymer chain to another.

crystal defect

Any of a variety of disruptions in the regularity of a crystal structure.

crystalline solid

A solid with a well-defined shape because of the orderly arrangement of the atoms, molecules, or ions.

cubic closet packing

A crystal structure based on the face-centered cubic unit cell in which the layers have an *abcabc* . . . pattern.