Ch. 3: Bonding and Chemical Interactions

Question 1

Chemical bonds can be…

Answer 1

Ionic or covalent

Question 2

Elements form bonds to…

Answer 2

Attain a noble gas like electron configuration

Question 3

Octet Rule

Answer 3

States that elements will be most stable with 8 valence electrons. However, there are many exceptions to this rule:

• Elements w an incomplete octet are stable with fewer than 8 electrons and include H, He, Li, Be, and B
• Elements with an expanded octet are stable w more than 8 electrons and include all elements in period 3 or greater
• Compounds with an odd number of electrons cannot have 8 electrons on each element

Question 4

Ionic Bonds

Answer 4

Formed via the transfer of one or more electrons from an element with a relatively low ionization energy to an element w a relatively high electron affinity (🔺EN > 1.7). Usually between metals and nonmetals. Form Crystalline lattices– large, organized arrays of ions

Question 5

Ionic Compounds

Answer 5

Unique physical and chemical properties

• Tend to dissociate in water and other polar solvents
• Tend to have high melting points

Question 6

Covalent Bond

Answer 6

Formed via the sharing of electrons between 2 elements of similar electronegativities

Question 7

Bond Order

Answer 7

Refers to whether a covalent bond is a single bond, double bond, or triple bond. As bond order increases, bond strength increases, bond energy increases and bond length decreases

Question 8

Covalent Bond Characterization by Polarity

Answer 8

Nonpolar bonds: result in molecules in which both atoms have exactly the same electronegativity; some bonds are considered nonpolar when there is a very samll diff in electronegativity between the atoms (🔺EN < 0.5), even though they are technically slightly polar
Polar Bonds: Form when there is a significant diff in electronegativities (EN = 0.5 to 1.7), but not enough to transfer electrons and form an ionic bond. In a polar bond, the more electronegative element takes on a partial negative charge, and the less electronegative element takes on a partial positive charge

Question 9

Coordinate Covalent Bonds

Answer 9

Result when a single atom provides both bonding electrons while the other atom does not contribute any; coordinate covalent bonds are most often found in Lewis acid-base chemistry

Question 10

Lewis Dot Symbols

Answer 10

Chemical representation of an atom’s valence electrons

Question 11

Formal charges

Answer 11

Exist when an atom is surrounded by more or fewer valence electrons than it has in its neutral state (assuming equal sharing of electrons in a bond)

Question 12

Resonance Structures

Answer 12

For any molecule with a pi system of electrons, resonance structures exist; these represent all of the possible configurations of electrons- stable and unstable- that contribute to the overall structure

Question 13

Valence Shell Electron Pair Repulsion (VSEPR) theory

Answer 13

Predicts the 3D molecular geometry of covalently bonded molecules. In this theory, electrons-whether bonding or nonbonding-arrange themselves to be as far apart as possible from each other in 3D space, leading to characteristic geometries

Question 14

Nonbonding electrons…

Answer 14

Exert more repulsion than bonding electrons bc they reside closer to the nucleus

Question 15

Electronic Geometry

Answer 15

Refers to the position of all electrons in a molecule whether bonding or nonbonding

Question 16

Molecular Geometry

Answer 16

Refers to the position of only the bonding pairs of electrons in a molecule

Question 17

Polarity of Molecules

Answer 17

Dependent on the dipole moment of each bond and the sum of the dipole moment of each bond and the sume of the dipole moments in a molecular structure

• All polar molecules contain polar bonds
• Nonpolar molecules may contain nonpolar bonds, or polar bonds w dipole moments that cancel each other

Question 18

Sigma Bonds

Answer 18

Result of head to head overlap

Question 19

Pi Bonds

Answer 19

Result of the overlap of 2 parallel electron cloud densities

Question 20

Intermolecular Forces

Answer 20

Electrostatic attractions between molecules. They are significantly weaker than covalent bonds (which are weaker than ionic bonds)

Question 21

London Dispersion Forces

Answer 21

Weakest interactions, but are present in all atoms and molecules. As the size of the atom or structure increases, so does the corresponding London dispersion force

Question 22

Dipole-Dipole Interactions

Answer 22

Occur between the oppositely charged ends of polar molecules, are stronger than London forces; these interactions are evident in the solid and liquid phases, but negligible in the gas phase due to the distance between particles

Question 23

Hydrogen Bonds

Answer 23

Are a specialized subset of dipole-dipole interactions involved in intra- and intermlecular attraction; hydrogen bonding occcurs when hydrogen is bonded to one of 3 very electronegative- atoms (flourine, oxygen, or nitrogen)