Chemistry: Chapter 8

Question 1

define covalent bond

Answer 1

a bond formed when electrons are shared between atoms

Question 2

define molecule

Answer 2

a neutral group of atoms joined together by covalent bonds

Question 3

define diatomic molecule

Answer 3

a molecule consisting of two atoms

Question 4

define molecular compound

Answer 4

a compound that is composed of molecules

Question 5

define molecular formula

Answer 5

a chemical formula of a molecular compound that shows the kinds and numbers of atoms present in a molecule of a compound

Question 6

define single covalent bond

Answer 6

a bond formed when two atoms share a pair of electrons

Question 7

define structural formula

Answer 7

a chemical formula that shows the arrangement of atoms in a molecule or a polyatomic ion

each dash b/t a pair of atoms indicates a pair of shared electrons

Question 8

define unshared pair

Answer 8

a pair of valence electrons that Is not shared between atoms

Question 9

define double covalent bond

Answer 9

a bond in which two atoms share two pairs of electrons

Question 10

define triple covalent bond

Answer 10

a covalent bond in which three pairs of electrons are shared by two atoms

Question 11

define coordinate covalent bond

Answer 11

a covalent bond in which one atom contributes both bonding electrons

Question 12

define polyatomic ion

Answer 12

a tightly bound group of atoms that behaves as a unit and has a positive or negative charge

ex. NH4^+ or SO3^2-

Question 13

define bond dissociation energy

Answer 13

the energy required to break the bond b/t two covalently bonded atoms

usually expressed in kJ per mol of substance

Question 14

define resonance structure

Answer 14

one of the two or more equally valid electron dot structures of a molecule or polyatomic ion

Question 15

define molecular orbital

Answer 15

an orbital that applies to the entire molecule

Question 16

define bonding orbital

Answer 16

a molecular orbital that can be occupied by 2 electrons of a covalent bond

Question 17

define sigma bond

Answer 17

a bond formed when 2 atomic orbitals combine to form a molecular orbital that is symmetrical around the axis, which connects two atomic nuclei

Question 18

define pi bond

Answer 18

a covalent bond in which the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms

Question 19

define tetrahedral angle

Answer 19

a bond angle of 109.5 degrees that results when a central atom forms four bonds directed toward the center of a regular tetrahedron

Question 20

define VSEPR Theory

Answer 20

valence-shell electron-pair repulsion theory: because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible

Question 21

define hybridization

Answer 21

the mixing of several atomic orbitals to form the same total number of equivalent hybrid orbitals

Question 22

define nonpolar covalent bond

Answer 22

a covalent bond in which the electrons are shared equally by the two atoms

Question 23

define polar covalent bond (polar bond)

Answer 23

a covalent bond between atoms in which the electrons are shared unequally

Question 24

define polar molecule

Answer 24

a molecule in which one side of the molecule is slightly negative and the opposite side is slightly positive

Question 25

define dipole

Answer 25

a molecule that has two poles, or regions, with opposite charges

Question 26

define van de waals forces

Answer 26

the two weakest intermolecular attractions - dispersion interactions and dipole forces

Question 27

define dipole interaction

Answer 27

intermolecular forces resulting from the attraction of oppositely charged regions of polar molecules

Question 28

define dispersion force

Answer 28

attractions between molecules caused by the electron motion on one molecule affecting the electron motion on the other through electrical forces these are the weakest interactions between molecules

Question 29

define hydrogen bond

Answer 29

attractive forces in which a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom

Question 30

define network solid

Answer 30

a solid in which all of the atoms are covalently bonded to each other

Question 31

what information does a molecular formula provide?

Answer 31

it shows how many atoms of each element a substance contains

Question 32

what representative units define molecular compounds and ionic compounds?

Answer 32

molecular compounds = a molecule ionic compounds = formula unit

Question 33

what is the result of electron sharing in covalent bonds?

Answer 33

to attain the electron configuration of a noble gases atoms also form double or triple covalent bonds if they can attain a noble gas structure by sharing two pairs or three pairs of electrons

Question 34

how are coordinate covalent bonds different from other covalent bonds?

Answer 34

in a coordinate covalent bond, the shared electron pair comes from one of the bonding atoms

Question 35

what are some exceptions to the octet rule?

Answer 35

the rule can't be satisfied in molecules whose total number of valence electrons is an odd number there are molecules in which an atom has less, or more, than a complete octet of valence electrons

Question 36

how is the strength of a covalent bond related to its bond dissociation energy?

Answer 36

a large bond dissociation energy corresponds to a strong covalent bond

Question 37

how are resonance structures used?

Answer 37

chemists use resonance structures to envision the bonding in molecules that cannot be adequately described by a single structural formula

Question 38

how are atomic and molecular orbitals related?

Answer 38

just like an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole

Question 39

what do scientists use the VSEPR theory for?

Answer 39

to explain the 3-D shape of molecules

Question 40

in what ways is orbital hybridization useful in describing molecules?

Answer 40

it provides information about both molecular bonding and molecular shape

Question 41

how do electronegativity values determine the charge distribution in a polar bond?

Answer 41

more electronegative atoms attract electrons more strongly and gains a slightly negative charge the less electronegative atom has a slightly positive charge

Question 42

what electronegativity difference range applies to nonpolar covalent bonds?

Answer 42

0.0-0.4

Question 43

what electronegativity difference range applies to moderately polar covalent bonds?

Answer 43

0.4-1.0

Question 44

what electronegativity difference range applies to very polar covalent bonds?

Answer 44

1.0-2.0

Question 45

what electronegativity difference range applies to ionic bonds?

Answer 45

≥ 2.0

Question 46

how do the strengths of intermolecular attractions compare with ionic and covalent bonds?

Answer 46

intermolecular attractions are weaker than either ionic or covalent bonds

Question 47

why are the properties of covalent compounds so diverse?

Answer 47

because of widely varying intermolecular attractions

Question 48

characteristics of ionic compounds? (7) ``` representative unit? bond formation? type of elements? physical state? melting point? solubility in water? good/bad conductors of electric current? ```

Answer 48

1. the representative unit is a formula unit 2. the bond formation is a transfer of electrons 3. the type of elements are metallic and nonmetallic 4. the physical state is a solid form 5. the melting point is very high 6. the solubility in water is usually high 7. they are good conductors of electric current

Question 49

characteristics of molecular compounds? (7) ``` representative unit? bond formation? type of elements? physical state? melting point? solubility in water? good/bad conductors of electric current? ```

Answer 49

1 molecule 2. sharing electrons b/t atoms 3. nonmetallic 4. solid, liquid, or gas 5. low 6. high to low 7. poor to nonconductors

Question 50

where are the electrons in covalent bonds?

Answer 50

in molecular orbitals - atomic orbitals that supply an area for electrons to be shared

Question 51

difference between linear and bent shapes?

Answer 51

linear doesn't have any lone paired electrons; lone paired electrons make the linear shape bend, therefore, it's bent

Question 52

Weakest electronegative element? What is it's value?

Answer 52

Cesium - 0.7 --> Least tendency to attract electrons

Question 53

Strongest electronegative element? What is it's value?

Answer 53

Fluorine - 4.0 --> has strong tendency to attract electrons