Bonding and Chemical Interactions

Question 1

What is the octet rule?

Answer 1

atoms tend to bond with atoms atoms so that it has eight electrons in its outermost shell

Question 2

Which elements have incomplete octets?

Answer 2

Hydrogen (2), helium (2), lithium (2), beryllium (4) and boron (6) - all stable with less than 8 valence electrons

Question 3

Which elements have expanded octets?

Answer 3

Any element in period 3 or greater

Question 4

What is ionic bonding?

Answer 4

one or more electrons from an atom with a low ionization energy, typically a metal, are transferred to an atom with a high electron affinity, typically a nonmetal

Question 5

What is covalent bonding?

Answer 5

an electron pair is shared between two atoms, typically nonmetals, that have relatively similar values of electronegativity

Question 6

What is a coordinate covalent bond?

Answer 6

when both of the shared electrons are contributed by only one of the atoms

Question 7

What is nonpolar vs polar mean in covalent bonding?

Answer 7

Nonpolar bonds are those that share the electrons equally and polar bonds do not which is determined by electronegativity

Question 8

Cation vs anion

Answer 8

Cation loses electrons and anion gains them in ionic bonding

Question 9

Characteristics of ionic compounds

Answer 9

• high melting/boiling points
• dissolve readily in polar solvents
• good electricity conductors when molten/aqueous
• form crystalline lattice in solid form

Question 10

Characteristics of covalent compounds

Answer 10

• low melting/boiling points

- poor conductors of electricity

Question 11

What is bond order?

Answer 11

the number of shared electron pairs between two atoms; single, double or triple bonds

Question 12

What is bond length?

Answer 12

the average distance between the two nuclei of atoms in a bond; gets shorted with each shared electron pair

Question 13

What is bond energy?

Answer 13

the energy required to break a bond by separating its components into their isolated, gaseous atomic states; the more electron pairs, the harder it is to break

Question 14

What is polarity?

Answer 14

occurs when two atoms have a relative difference in electronegativities; atom with higher electronegativity gets larger share of electron density

Question 15

What difference in electronegativity is necessary to be nonpolar?

Answer 15

less than 0.5

Question 16

What is a dipole moment?

Answer 16

A way of describing the difference in electronegativies that result from polar molecules. A dipole moment is indicated by an arrow in which the head points toward the more electronegative element with the partial negative charge and the other end of the arrow with the + sign is at the less electronegative element with a the partial positive charge.

Question 17

What is the equation for a dipole moment?

Answer 17

p = qd
p = dipole moment
q = magnitude of the charge
d = displacement vector separating the two partial charges

Question 18

What is a Lewis acid?

Answer 18

any compound that will accept a lone pair of electrons

Question 19

What is a Lewis base?

Answer 19

any compound that will donate a pair of electrons to form a covalent bond

Question 20

What is the equation for formal charge?

Answer 20

formal charge = V - Nnonbonding - 1/2Nbonding
V = normal number of electrons in atoms valence shell
Nnonbonding = the number of electrons that are not being used in a bond
Nbonding = the number of electrons that are being used in a bond

Question 21

Resonance structures

Answer 21

multiple Lewis structures that demonstrate the same arrangement of atoms but differ in the specific placement of the electrons

Question 22

What is the VSEPR shape and angles for a compound with 2 electron density clouds?

Answer 22

linear; 180 degrees

Question 23

What is the VSEPR shape and angles for a compound with 3 electron density clouds?

Answer 23

trigonal planar; 120 degrees

Question 24

What is the VSEPR shape and angles for a compound with 4 electron density clouds?

Answer 24

tetrahedral/trigonal pyramidal; 109.5 degrees

Question 25

What is the VSEPR shape and angles for a compound with 5 electron density clouds?

Answer 25

trigonal bipyramidal; 90, 120 and 180 degrees

Question 26

What is the VSEPR shape and angles for a compound with 6 electron density clouds?

Answer 26

octahedral; 90, 180 degrees

Question 27

Electronic geometry vs molecular geometry

Answer 27

Electronic geometry - describes the spatial arrangement of all pairs of electrons around the central atom; including both bonding and lone pairs
Molecular geometry - describes the spatial arrangement of only the bonding pairs of electrons

Question 28

Order the intermolecular forces from strongest to weakest

Answer 28

Hydrogen bond > dipole-dipole interactions > dispersion/London forces

Question 29

What are London Dispersion forces?

Answer 29

attractive or repulsive interactions based on short-lived and rapidly shifting dipoles which are formed due to polarization and counterpolarization of interacting electron clouds

Question 30

What are dipole-dipole interactions?

Answer 30

When the positive region of a molecule is close to the negative region of another this forms an attractive electrostatic force; present in liquid and solid but not gas phases

Question 31

What is the difference between London dispersion forces and dipole dipole interactions?

Answer 31

Both are electrostatic forces between opposite partial charges; the DIFFERENCE is only in the permanence/duration of the molecular dipole

Question 32

What are hydrogen bonds?

Answer 32

a specific, unusually strong form of dipole-dipole interactions. The positive hydrogen will interact with negative charges on other atoms