Chemistry Ch 5

what four covalent bonds can carbon form?

-four single bonds -two single bonds and one double bond -two double bonds -one triple bond and one single bond

deca-

10 ex: P_4Se_10 = tetraphosphorus decaselenide

oxygen has 6 valence electrons and thus needs ________ more electrons to obey the octet rule

2

di-

2 ex: O_2F_2 = dioxygen difluoride

in Lewis structures depicting covalent bonding, an "octet" of electrons for atoms of H means

2 electrons

the Lewis structure for a N_2 molecule contains a triple bond, and a total of 10 valence electrons. How many nonbonding electrons are present in the Lewis structure for this molecule?

2 electrons

how many hydrogen atoms (1 valence electron) would be expected to bond a phosphorus atom (5 valence electrons) during covalent compound formation?

3

nitrogen has 5 valence electrons and thus needs _________ more electrons to obey the octet rule

3

tri-

3 -PCl_3 = phosphorus trichloride

the number of single, double, and triple covalent bonds present, respectively, in a molecule whose Lewis structure is HOOH is

3, 0, 0

given that P has five valence electrons and O has six valence electrons, how many total valence electrons are present in the Lewis structure for the PO_4^3- ion?

32 electrons

carbon has 4 valence electrons and thus needs ________ more valence electrons to obey the octet rule

4

tetra-

4 -N_2O_4 = dinitrogen tetroxide

penta-

5 ex: ClF_5 = chlorine pentafluoride

the number of electrons present in a triple bond is

6

hexa-

6 ex: I_2F_6 = diiodine hexafluoride

how many nonbonding valence electrons are present in the Lewis structure H-F?

6 (fluorine has 7 electrons, hydrogen as 1, they form a covalent bond to complete their outer shells thus sharing a pair of electrons, so 6 are left over)

hepta-

7 ex: IF_7 = iodine heptafluoride

octa-

8 ex: P_4O_8 = tetraphosphorus octoxide

nona-

9 ex: P_4S_9 = tetraphosphorus nonsulfide

both Cl and F atoms contain 7 electrons; the expected chemical formula for the simplest covalent bond formed between these two elements is...

ClF (share one electron each, forming one pair of electrons shared = covalent bond = 8 electrons in outer shell)

most electronegative element

Fluorine (4.0)

ionic bond

Formed when one or more electrons are transferred from one atom to another; the resulting oppositely charged ions creates are attracted to each other resulting in a bond -electron goes to the most electronegative atom

selected binary molecular compounds that have common names

H_2O = water H_2O_2 = hydrogen peroxide NH_4 = ammonia N_2H_4 = hydrazine CH_4 = methane C_2H_6 = ethane N_2O = nitrous oxide NO = nitric oxide

octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons; aka noble-gas configuration

which of the following in an incorrect statement about coordinate covalent bonds? a. both atoms involved in the bond contribute an equal number of electrons to the bond b. both electrons of a shared electron pair come form the same atom c. once formed, they are indistinguishable from other covalent bonds

a

covalent bond

a chemical bond resulting from two nuclei attracting the same shared electrons

VSEPR electron group

a collection of valence electrons present in a localized region about the central atom in a molecule -may contain two, four, or six electrons (single, double, or triple bonds)

nonpolar covalent bond

a covalent bond in which there is equal sharing of electrons between two atoms

molecular geometry

a description of the three-dimensional arrangement of atoms within a molecule -important factor in determining the physical and chemical properties of a substance

molecular polarity

a measure of the degree of inequality in the attraction of bonding electron to various locations within a molecule -if one part of a molecule is favored over other parts, it is said to be polar

bond polarity

a measure of the degree of inequality in the sharing of electrons between two atoms in a chemical bond

electronegativity

a measure of the relative attraction that an atom has for the shared electrons in a bond -the higher this number, the greater the attraction of atoms

delta notation

a method of indicating a partial positive and a partial negative charge in a chemical bond

diatomic molecule

a molecule containing only two atoms -simplest type of molecule

valence shell electron pair repulsion (VSEPR) theory

a set of procedures for predicting the molecular geometry of a molecule using the information contained in the molecule's Lewis structure

molecular polarity of trigonal planar and tetrahedral

a) molecules in which all of the atoms attached to a central atom are identical (ex. SO_3 or CH_4) = nonpolar -the individual bond polarities cancel as a result of the highly symmetrical arrangements of atoms around a central atom b) if 2 or more kinds of atoms are attached to the central atom in a trigonal planar or tetrahedral molecule, the molecule is polar (symmetry of polarity is not present) - ex. if one hydrogen (electronegativity 3.1) in CH_4 was replaced by Chlorine (electronegativity = 3.0) a polar molecule results

which of the following molecules, all of which are linear, is nonpolar? a. carbon dioxide (OCO) b. hydrogen cyanide (HCN) c. dinitrogen monoxide (NNO)

a. carbon dioxide

in general metallic elements ahve

about the same electronegatives as nonmetallic elements

noble gas configuration

an outer main energy level fully occupied, in most cases, by eight electrons (unless H and He = 2 valence electrons)

in a polar molecule there is

an unsymmetrical distribution of electronic charge

2 bonding, 1 nonbonding VSEPR groups

angular

2 bonding, 2 nonbonding VSEPR groups

angular

which of the following concepts is closely associated with the covalent bond model?

attraction of two nuclei for shared valence electrons

in a completed Lewis structure for a molecular compound all atoms a. must have an octet of electrons b. except hydrogen must have an octet of electrons c. except hydrogen and oxygen must have an octet of electrons

b

based on the given molecular geometry, which of the following molecules is nonpolar? a. NF_3 (trigonal pyramidal) b. CH_4 (tetrahedral) c. H_2S (angular)

b. (tetrahedral w/ identical atoms around central atom have symmetrical polarity = they can cancel each other out)

which of the following binary molecular compounds is paired w/ an incorrect common name? a. NO = nitric oxide b. NH_3 = hydrazine c. H_2O_2 - hydrogen peroxide

b. (the rest are common names)

the term multiple covalent bond applies to

both double and triple bonds

both ionic and covalent bonding are present in which of the following chemical species? a. SO_4^2- ion b. H_2SO_4 c. Na_2SO_4

c

in covalent bond formation, the two atoms sharing electrons a. must be identical b. must be different c. can be the same or different

c.

which of the following characterizations for the bond line in the Lewis structure H-F is incorrect? a. it represents two shared electrons b. it represents a covalent bond c. it represents an octet of electrons

c.

which of the following compounds has molecules as its basic structural unit? a. FeO b. Al_2O_3 c. SCl_3

c. (bc its a molecular compound - has two nonmetals covalently bonded - and thus is basic structural unit is molecules)

which of the following compounds would be expected to contain covalent bonds? a. CuCl_2 b. FeCl_2 c. SCl_2

c. (both are nonmetal atoms)

in which of the following situations is an incorrect numerical prefix present in the compound's name? a. N_2O_3 = dinitrogen trioxide b. NO_2 = nitrogen dioxide c. N_2O_5 = dinitrogen tetroxide

c. (should be dinitrogen pentoxide)

which of the following compounds is a binary molecular compound? a. HCN b. NaCl c. CO_2

c. CO_2

which of the following is not a normal bonding behavior for oxygen atoms (six valence electrons)? a. formation of two single bonds b. formation of one double bond c. formation of two double bonds

c. formation of two double bonds

which of the following is not a possible molecular geometry for molecules that have four electron groups about a central atom? a. tetrahedral b. trigonal pyramidal c. trigonal planar

c. trigonal planar

molecules containing polar covalent bonds

can be polar or nonpolar depending on molecular geometry

what's the correct name for compound CO?

carbon monoxide

as the difference in electronegativity between two bonded atoms decreases the bond becomes more

covalent

the bonding within a polyatomic ion is

covalent **ionic bonding between it and ions of opposite charge

coordinate covalent bonds

covalent bond in which both electrons in a shared pair of electrons come from one of the two atoms in the bond ex: HOClO forming into HClO_2 (oxygen has 2 vacancies in its valence shell, so it uses a nonbonding pair of electrons on the Cl atom to meet its "electron needs" - Cl atom still has its existent octet of electrons)

polar covalent bond

covalent bond in which there is an unequal sharing of electrons between two atoms -the electrons spend more time nearer to the more electronegative nucleus -creates fractional positive and negative charges on atoms (significantly affects molecular properties)

single covalent bond

covalent bond in which two atoms share one pair of electrons

triple covalent bond

covalent bond in which two atoms share three pairs of electrons -three times as strong as a single -most common: N2

double covalent bond

covalent bond in which two atoms share two pairs of electrons -twice as strong as single (takes twice as much energy to break as a single)

which of the following diatomic molecules is polar a. H2 b. F2 c. N2 d. no correct answer

d. (diatomic molecules are always nonpolar)

in Lewis dot structures, the shared electrons are represented by...

dashes

ionic bonds form between atoms of _________ elements

dissimilar (metal and nonmetal)

covalent bonds form by the sharing of electrons thru an overlap of _______________

electron orbitals

central concept of VSEPR theory

electron pairs in the valence shell of an atom adopt an arrangement in space that minimizes the repulsions between like-charged (all negative) electron pairs

names for binary molecular compounds, except for a few common names, always...

end with the suffix -ide

the number of single, double, and triple covalent bonds present, respectively, in a molecule whose Lewis structure is H:C:::N: is

1, 0, 1

systematic procedure for drawing a Lewis Structure

1. calculate the total number of valence electrons available in the molecule by adding together the valence electron counts for all atoms in the molecule 2. write the chemical symbols of the atoms in the molecule in the order in which they are bonded to one another, and then place a single covalent bond, involving two electrons, between each pair of bonded atoms 3. add nonbonding electron pairs to the structure such that each atom bonded to the central atom has an octet of electrons; remember that for hydrogen, an "octet" is only 2 electrons 4. place any remaining electrons on the central atom of the structure 5. if there are not enough electrons to give the central atom on octet, then use one or more pairs of nonbonding electrons on the atoms bonded to the central atom to form double or triple bonds 6. count the total number of electrons in the completed Lewis structure to make sure it is equal to the total number of valence electrons available for bonding as calculated in step 1

drawing lewis structures for polyatomic ions

1. count the number of valence electrons for each atom and add them up 2. find the charge on the polyatomic ion to know if extra electrons are present or if electrons are missing 3. draw the molecular skeleton w/ single covalent bonds between bonded atoms 4. add nonbonding electron pairs to give each atom an octet 5. put the polyatomic structure in a bracket and add the charge as a superscript on the right side

geometry of molecules operation rules

1. draw a Lewis structure for the molecule 2. count the number of VSEPR electron groups about the central atom in the Lewis structure 3. assign a geometry based on minimizing repulsions between electron groups

operational rules with use of VSEPR theory

1. draw a lewis structure for the molecule & identify the specific atom for which geometrical information is desired (this atom will usually be the central atom in a molecule( 2. determine the number of VSEPR electron groups present about the central atom; following conventions govern this decision: a. no distinction is made between bonding and nonbonding electron groups; both are counted b. single, double, and triple bonds are all counted equally as "one electron group" bc each takes up only one region of space about a central atom 3. predict the VSEPR electron group arrangment about hte atom by assuming that the electron groups orient themselves in a manner that minimizes repulsions

molecular polarity of linear triatomic molecules

example: CO2, both bonds are polar (oxygen is more electonegative than carbon) but CO2 molecule is nonpolar bc the effects of the 2 polar bonds cancel each other out bc oxygen atoms are arranged symmetrically around carbon atom; one end of the molecule is not negatively charged relative to the other end (requirment for polarity) example 2: HCN is linear, but polar, both bond polarities contribute to nitrogen's acquiring a partial negative charge relative to hydrogen

molecular polarity of angular triatomic molecules

example: H2O is polar bc the bond polarities associated w/ the two hydrogen-oxygen bonds do not cancel one another bc of the nonlinearity of the molecule

prefix mono-

never used to modify the name of the first element in the compounds name, but is used to modify the name of the first element in the compound's name ex: the name of the compound CO is carbon monoxide rather than monocarbon monoxide

Carbon has four valence electrons and H has one valence electron; the Lewis structure for the CH_4 molecule contains how many nonbonding electrons?

none

bond that involve atoms w/ similar electronegativities (difference of 0.4 or less) are...

nonpolar covalent bonds

molecular compounds in which hydrogen is the first listed element in the formula are named without __________

numerical prefixes ex: H_2S and HCl are hydrogen sulfide and hydrogen chloride, respectively

molecular polarity of diatomic molecules

only one bond present -if bond polar, then molecule is polar -if bond nonpolar, then molecule is nonpolar

the electronegativities of the elements C, N, and O are, respectively, 2.5, 3.0, and 3.5; which of these elements exerts the greatest influence on the shared electrons in a covalent bond

oxygen

nonbonding electrons (aka unshared electron pairs or lone electron pairs)

pairs of valence electrons on an atom that are not involved in electron sharing

bonding electrons

pairs of valence electrons that are shared between atoms in a covalent bond

covalent bonds form between atoms of ____________ elements

similar (both nonmetals) or identical (the same nonmetal)

all ionic compounds are _______ at room temp

solid

4 bonding VSEPR groups

tetrahedral

molecules w/ four VSEPR electron groups are either

tetrahedral (no bonding electron groups present) trigonal pyramidal (one nonbonding electron group present) angular (two nonbonding electron groups present)

name the following: P_4O_10

tetraphosphorus decoxide

for the molecule :N=-N-O: (O has 6 dots around it), the concept of a coordinate covalent bond is needed to explain the bonding between

the N and O atoms

in a polar covalent bond the notation called a "delta plus symbol" is assigned to

the atom with the smallest electronegativity

bonds w/ electronegativity difference between 1.5 and 2.0 are considered ionic if...

the bond involves a metal and a nonmetal

bonds w/ electronegativity difference between 1.5 and 2.0 are considered polar covalent if...

the bond involves two nonmetals

rule used when constructing names of binary molecular compounds

the full name of the nonmetal of lower electronegativity is given first, followed by a separate word containing the stem of the name of the more electronegative nonmetal and the suffix "-ide" -numerical prefixes, giving numbers of atoms, precede the names of both nonmetals

to complete its octet by electron sharing, an oxygen atom can form either _____ single bonds or _____ double bond

two; one

the degree of inequality in electron sharing for a nonpolar covalent bond is

very small or zero (less than 0.4)

molecules w/ more than one central atom

zero bends, two bends, and one bend in the four atom chain

t or f: electron sharing can occur only when electron orbitals from two different atoms overalp

true -once they overlap, the most favorable location for electrons is directly between the nuclei -this situation provides increased stability

t or f: in the Lewis structure for an ionic compound that contains a polyatomic ion, the positive and negative ions are treated separately to show that they are individual ions not linked by covalent bonds

true ex: in the Lewis structure of potassium sulfate, K_2SO_4 is written w/ brackets around the SO_4 and the 2 K+

t or f: ionic compounds do not contain discrete molecules

true! -they consist of an extended array of alternating positive and negative ions

t or f: in covalently bonded compounds, the basic structural unit is a molecule

true! -that is why they are sometimes called molecular compounds

t or f: the electronegativity values increase from left to right across periods and from bottom to top across groups

true; nonmetals generally having higher electronegativity -metals (low electronegatives, poor electron attractors) give up electrons to nonmetals (high electronegatives, good electron attractors)

the Lewis structure for a H_2S molecule contains eight valence electrons, four of which are nonbonding; how many single and double bonds are present, respectively, in this molecule?

two and zero

in VSEPR theory, an angular molecular geometry is associated w/ molecules in which the central atom has

two bonding groups and two nonbonding groups

carbon dioxide lewis structure1

two double bonds

molecular polarity depends on...

1. bond polarities 2. molecular geometry

mono-

1 ex: CO = carbon monoxide

linear electron geometry

two electron pairs, to be as far as part as possible, are found on opposite sides of the nucleus - 180 degree angle to one another

pure (nonpolar) covalent bond

formed between identical atoms (exact same electronegativity)

basic structural unit of an ionic bond

formula unit

carbon atoms normally form four covalent bonds; this is indicative of the presence of how many vacancies in the valence electron shell of carbon atoms?

four

tetrahedral electron geometery

four electron pairs are arranged into a four-sided solid inwhich all four sides are identical equilateral triangles; the angel between any two electron pairs is 109 degrees

in a polar covalent bond the atom of greater electronegativity bears a...

fractional negative charge

name the following: HBr

hydrogen bromide (no prefixes when H is first)

what's the correct name for the compound HF?

hydrogen fluoride

electronegativity values of the elements

increase across a period in the periodic table

as the polarity of the bond increases, the bond is increasingly _________

ionic

bonds w/ electronegativity difference greater than 2.0 are...

ionic bonds

2 bonding VSEPR groups

linear

molecules with two VSEPR electron groups are

linear

binary molecular compound

molecular compound in which only two nonmetallic elements are present

nonpolar molecule

molecule in which there is a symmetrical distribution of electron charge

polar molecule

molecule in which there is an unsymmetrical distribution of electronic charge

a chemical bond for which the electronegativity difference between atoms is 1.2 is classified as a

polar covalent bond

bonds w/ electronegativity difference greater than 0.4 but less than 1.5 are...

polar covalent bonds

the numerical value of electronegativity difference between two bonded atoms gives an approximate measure of the ______ of the bond

polarity greater numerical difference = greater the inequality of electron sharing = greater polarity

names for binary molecular compounds usually contain numerical ______________ that give the number of each type of atom present in addition to the names of the elements present

prefixes

t or f: there is a strong tendency for nonmetals to form a specific number of covalent bonds; the number of bonds formed is equal to the number of electrons the nonmetal atom must share to obtain an octet of electrons

true

t or f: when writing the Lewis structure of an ion (monatomic or polyatomic) it is customary to sue brackets and to show the ionic charge outside of the brackets

true

covalent bond formation most often involves electron sharing between

two nonmetal atoms

the concept of electronegativity can be used to determine...

the relative attraction of an atom for shared electrons in a bond

Lewis symbol

the representation of an atom that shows valence electrons as dots around the symbol of the element

during covalent bond formation, there is a strong tendency for atoms of nitrogen to form...

three covalent bonds

trigonal planar electron geometry

three electron pairs are as far apart as possible when they are found at the corners of an equilateral triangle; separated by 120 degree angles

Nitrogen has five valence electrons and Cl has seven valence electrons; the Lewis structure for the molecule NCl_3 contains

three single bonds

3 bonding VSEPR groups

trigonal planar

in VSEPR theory, the geometric arrangment that minimizes repulsions among three valence electron pairs on a central atom is...

trigonal planar

molecules with three VSEPR electron groups are either...

trigonal planar or angular trigonal planar: all three VSEPR groups are bonding angular: one of the three VSEPR groups are nonbonding

3 bonding, 1 nonbonding VSEPR groups

trigonal pyramidal

t or f: VSEPR electron group arrangement and molecular geometry are not the same when a central atom possesses nonbonding electron pairs; the word used to describe the molecular geometry in such cases does not include the positions of the nonbonding electron groups

true

t or f: a molecular compound that is soluble in water produces a nonconducting aqueous solution

true

t or f: an ionic solid that is soluble in water produces an electrically conducting aqueous solution

true

t or f: molecular compounds may be solid, liquid, or gas at room temp

true

t or f: most bonds are a mix of ionic and covalent bonds

true

t or f: once a coordinate covalent bond forms, it is indistinguishable form other covalent bonds in a molecule

true

t or f: polyatomic ion charge is not localized on a particular atom, but rather is associated w/ the ion as a whole

true