Chapter 10 Vocab

Question 1

Lewis structure

Answer 1

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

Question 2

Resonance structure

Answer 2

(Also resonance 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.

Question 3

Resonance hybrid

Answer 3

The weighted average of the resonance structures for a species.

Question 4

Electron-pair delocalization

Answer 4

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

Question 5

Formal charge

Answer 5

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

Question 6

Electron deficient

Answer 6

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

Question 7

Free radical

Answer 7

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

Question 8

Expanded valence shell

Answer 8

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.

Question 9

Valence-shell electron-pair repulsion (VSEPR) theory

Answer 9

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

Question 10

Molecular shape

Answer 10

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

Question 11

Bond angle

Answer 11

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.

Question 12

Linear arrangement

Answer 12

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

Question 13

Linear shape

Answer 13

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

Question 14

Trigonal planar arrangement

Answer 14

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°).

Question 15

Bent

Answer 15

(Also 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 has the AX2E2 shape class (bond angle < 109.5°) in the tetrahedral arrangement.

Question 16

Tetrahedral arrangement

Answer 16

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°).

Question 17

Trigonal pyramidal shape

Answer 17

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

Question 18

Trigonal bipyramidal arrangement

Answer 18

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°).

Question 19

Equatorial group

Answer 19

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

Question 20

Axial group

Answer 20

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.

Question 21

Seesaw shape

Answer 21

A molecular shape caused by the presence of one equatorial lone pair in a trigonal bipyramidal arrangement (AX4E; bond angles < 120° and 90°).

Question 22

T-shaped

Answer 22

A molecular shape caused by the presence of two equatorial lone pairs in a trigonal bipyramidal arrangement (AX3E2; bond angles < 90°).

Question 23

Octahedral arrangement

Answer 23

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°).

Question 24

Square pyramidal shape

Answer 24

A molecular shape (AX5E) caused by the presence of one lone pair in an octahedral electron-group arrangement (bond angles < 90°).

Question 25

Square planar shape

Answer 25

A molecular shape (AX4E2) caused by the presence of two lone pairs at opposite vertices in an octahedral electron-group arrangement (bond angles 90°).

Question 26

Molecular polarity

Answer 26

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

Question 27

Dipole moment (μ)

Answer 27

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).