smartbook 13

which of the following statements correctly describe the 'normal' bonding pattern for a neutral atom of each element, assuming that the octet rule is obeyed?

-C usually forms four covalent bonds -F always form a single covalent bond -H forms one covalent bond and is generally not found as a central atom is covalent species

which of the following statements correctly describe KBr2?

-Kr is surrounded by 3 lone pairs -Kr is surrounded by 5 electron pairs

which of the following statements correctly describe the effect of molecular polarity on the behavior of a molecular compound?

-a polar compound will experience stronger intermolecular forces than a nonpolar compound -the physical properties of a molecular compound are directly related to molecular polarity

which of the following statements correctly describe the relative stabilities of resonance forms?

-a resonance structure with formal charges closer to zero on individual atoms is preferred -a resonance structure is more stable if a negative charge resides on a more electronegative atom

in a lewis structure ________

-bonding electrons pairs are shown as lines -lone pairs are shown as pairs of dots

which option correctly describes a covalent species that has four electron groups around the central atom?

-if all four electron pairs are bonding pairs, the shape of the system is tetrahedral -a bent shape is observed if there are two bonding pairs and two lone pairs -the ideal bond angle for a four electron system is 109.5

which of the following statements correctly describe resonance structures?

-resonance structure differ only in the arrangement of electrons -an individual resonance structure does not accurately represent the structure of the species

which of the following statements correctly describe formal charge?

-the formal charge of an atom is the charge it would have if all bonding electrons were shared equally -formal charges can be used to select the most important resonance structures for a species

a covalently species such as the molecule H2NO has more than one central atom. which of the following options correctly describe how to draw a lewis structure for this species?

-there will be three bonds to the N atom -the O atom will be bonded to both H and N -N and O are central atoms because both elements form more than one covalent bond

arrange the steps involved in drawing a lewis structure in the correct order

1.) count the valence electrons from all atoms, and add or subtract electrons according to the charge. place the atoms relative to each other 2.) place a bond between every pair of atoms, using two valence electrons for each bond 3.) distribute the remaining electrons in pairs to give each atom an octet (except for hydrogen) 4.) form multiple bonds if all electrons have been used and any atom does not have an octet

place the steps for determining the shape of a covalently bonded species in the correct order

1.) use the molecular formula to draw a Lewis structure 2.) count all electron groups and assign an electron-group arrangement 3.) determine the molecular shape by counting bonding and nonbonding groups separately

certain molecules are electron deficient, having fewer than _____ electrons around the central atom, which nonetheless has a formal charge of zero. elements that commonly form electron deficient gaseous compounds are beryllium and _____

8 ; boron/aluminum

which of the following elements may have an expanded valence shell? S, N, Xe, O, Cl

S, Xe, Cl

AX3E2

T-shaped

resonance structures are Lewis structures that have the same relative placement of _______ but a different arrangement of _____

atoms ; electrons

AX2E

bent

AX2E2

bent

to classify molecular shapes, a structure is assigned a specific AXmEn designation, where A is the _________ atom, X is a(n) _____ atom, and E represents a(n) _______ valence electron group that is usually a lone ____

central ; surrounding ; nonbonding ; pair

in a single, double, or triple bond, the shared electron pairs are localized between the bonded atoms. in a resonance hybrid, electrons are _________ or spread out over two or more adjacent atoms. instead of a double or triple bond between two such atoms, the bond is considered a(n) ____ double or triple bond with a fractional bond order

delocalized ; partial

the polarity of a molecule can be expressed in terms of its ______ moment, which is the product of the partial ______ in the molecules and the ______ between their centers

dipole ; charges ; distance

oxidation number

does not change for a particular atom from one resonance form to another

which statement correctly describes the basic principle of VSEPR theory?

each group of valence electrons around a central atom is located as far from the others as possible

a 5 electron group system has two different types of positions for substituents. the three positions marked "1" form a trigonal plane about the central atom and are called _______ positions while the two positions marked "2" are ______ positions. lone pairs prefer to occupy the ______ positions

equatorial ; axial ; equatorial

some elements do not obey the octet rule because they have more than eight valence electrons, i.e., they have a(n) ________ valence shell. this is only possible for elements that have available ___ orbitals, i.e., elements from period __ of the periodic table onward

expanded ; d ; 3

true or false : any molecule in which all of the bonds are identical will be nonpolar

false

true or false : resonance structures are different possible structures for the same species that interconvert rapidly

false

individual bond dipoles will cancel

for a species that has identical bonds and a symmetrical geometry

individual bond dipoles will not cancel

for a species with an unsymmetrical geometry

half the shared bonding electrons are assigned to each atom of the bond in order to calculate the :

formal charge

a species will be nonpolar overall

if individual bond dipoles cancel

a species will be polar overall

if individual bond dipoles do not cancel

AX2E3

linear

to show the bonding in a molecule or polyatomic ion, we can use a lewis structure, which shows bonding electron pairs as ________ and any nonbonding electrons as _______

lines ; dots

formal charge

may change for a particular atom from one resonance form to another

AX6

octahedral

a lewis structure will usually require one or more multiple bonds if there is an atom present that does not have a full _____ after all available electrons have already been placed. the multiple bond is formed by exchanging one ______ electron pair for each new bond

octet ; lone

all shared bonding electrons are assigned to the more electronegative atom in order to determine the :

oxidation number

consider the molecule CCl4-. each C-Cl bond in this molecule is ____ because the electronegativity difference between C and Cl is ______ than 0.4. since CCl4 is tetrahedral in shape and symmetrical, the individual bond dipoles ____ and the molecule is _____ overall

polar ; greater ; cancel ; nonpolar

AX4E

seesaw

AX4E2

square planar

AX5E

square pyramidal

in general, the smaller the bond angle, the _______ electron repulsions for the group concerned. in a five electron group system, lone pairs prefer to occupy _____ positions because equatorial-equatorial repulsions are ______ than axial-equatorial repulsions

stronger ; equatorial ; weaker

AX4

tetrahedral

AX5

trigonal bipyramidal

AX3

trigonal planar

AX3E

trigonal pyramidal

true or false : when using VSEPR theory to determine molecular shape, a triple bond counts as a single electron domain even though it consists of three shared electron pairs

true

a bond angle is the angle formed by the nuclei of ____ surrounding atoms with the nucleus of a central atom. the bond angle is predicted from the molecular shape is a(n) _____ bond angle. if the bonding electron groups around the central atom are not ____, the real bond angle will deviate from the predicted value

two ; ideal ; identical

some covalently bonded species do not obey the octet rule because they have an odd number of electrons. a species containing one or more _______ electrons is called a free radical. most odd electron molecules have a central atom from an odd numbered group, either group ______ or group ______

unpaired ; 5A ; 7A

the electron group arrangement around a central atom is defined by the number of ____-electron groups. the molecular shape is defined by the relative positions of the _____ around the central atom. two species may have the same electron-group arrangement but have different molecular shapes

valence ; atoms

the formal charge assigned to an atom is calculated by subtracting the number of electrons the atom "owns" from the total number of ______ electrons. the number of electrons owned by a specific atom is defined as being the sum of the ________ valence electrons and half the _____ valence electrons

valence ; unshared ; shared