Ch. 3 bonding and chemical interactions

chemical bonds can be ___ or ____

ionic, covalent

elements will form bonds to attain a

noble gas-like electron configuration

the octet rule states that

elements will be most stable with eight valence electrons

what are the exceptions to the octet rule

1. elements with an incomplete octet are stable with fewer than eight electrons and include H, He, Be, B

2. elements with an expanded octet are stable with more than eight electrons and include all elements in period 3+

3. compounds with an odd number of electrons cannot have eight electrons on each elements

an ___ bond is formed via the transfer of one or more electrons from an element with a relatively low ionization energy to an element with a relatively high electron affinity

ionic

ionic bonds occur between elements with large differences in electronegativity (>__), usually between metals and nonmetals

1.7

a positively charged ion is called a ____, a negatively charged ion is called an _____

cation, anion

the resulting electrostatic attraction between ions causes them to

remain in close proximity, forming the bond

ionic compounds form ____ ____ → large, organized arrays of ions

crystalline lattices

ionic compounds tend to dissociate in ____ and other polar solvents

water

ionic solids tend to have ____ melting points

high

a ____ bond is formed via the sharing of electrons between two elements of similar electronegativities

covalent

bond order refers to whether a covalent bons is a

single bond, double bond, or triple bond

as bond order increases, bond strength _____, bond energy _____, and bond length _____

increases, increases, decreases

covalent bonds can be categorized as

polar or nonpolar

____ bonds result in molecules in which both atoms have exactly the same electronegativity; some bonds are considered nonpolar when there is a very small difference in electronegativity between the atoms (<0.5)

nonpolar

_____ bonds form when there is a significant difference in electronegativities (0.5-1.7). The more electronegative element takes on a partial negative charge, and the less electronegative element takes on a partial positive charge

polar

coordinate covalent bonds result when a

single atom provides both bonding electrons while the other atom does not contribute any (often found in Lewis acid-base chemistry)

Lewis dot symbols are

chemical representation of an atom’s valence electrons

formal charges exist when an atom is

surrounded by more or fewer valence electrons than it has in neutral state

for any molecule with a ____ system of electrons, resonance structures exist

π (pi)

the valence shell electron pair repulsion (VSEPR) theory predicts the 3D molecular geometry of covalently bonded molecules. In this theory, electrons arrange themselves to be

as far apart as possible from each other in 3D space

non bonding electrons exert ___ repulsion than bonding electrons because they reside closer to the nucleus

more

electric geometry refers to the

position of all electrons in a molecule, whether bonding or nonbonding

molecular geometry refers to the

position of only the bonding pairs of electrons in a molecule

the polarity of molecules is dependent on the

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

all polar molecules contain ___ bonds

polar

nonpolar molecules may contain ____ bonds, or ____ bonds, with dipoles moments that cancel each other

nonpolar, polar

σ and π bonds describe the patterns of

overlap observed when molecular bonds are formed

Sigma σ bonds are the result of

head-to-head overlap

Pi π bonds are the result of

overlap of two parallel electron cloud densities

intermolecular forces are

electrostatic attractions between molecules. They are weaken than covalent bonds (which are weaker than ionic bonds)

London dispersion forces are

the weakest interactions, but are present in all atoms and molecules

dipole-dipole interactions are

stronger than London forces; these interaction are evident in the solid and liquid phases but negligible in gas phase due to the distance between particles

hydrogen bonds are

a specialized subset of dipole-dipole interaction involved in intro- and intermolecular attraction; hydrogen bonding occurs when hydrogen is bonded to one of three very electronegative atoms (Fluorine, Oxygen, Nitrogen)