Unit 2: Molecular & Ionic Compound Structure & Properties

covalent bonds

chemical bonds formed from sharing valence electrons between 2 atoms

nonpolar covalent bonds

form between two nonmetals of similar EN

ionic bonds

chemical bonds formed from the electrostatic force between 2 oppositely charged ions, forming ionic compounds (aka “salts”)

lattice energy

energy required to completely separate 1 mole of a solid ionic compound into its constituent gaseous ions

ionic solids

form a lattice/crystal structure and have high MP/BPs

metallic solids

form a crystal array of nuclei with core electrons while the valence electrons are “delocalized” and free to move throughout the solid

substitutional alloy

mix two transition metals together - additional element replaces original metal atoms

interstitial alloy

additional element occupies gaps between original metal atoms

bond energy

measure of the strength of a chemical bond

delocalized electrons

electrons that aren’t stuck in one specific spot, but can move around over several atoms or a larger structure

“shared electrons” that roam freely in a molecule or material

electron groups

#bonding groups + #lone pairs

bonding groups

pair of electrons shared between 2 atoms

lone pair

pair of electrons that belong to one atom

resonance structures

lewis structures that show multiple possible arrangements of electrons in a molecule/ion

formal charge

system used to calculate the relative stability of a lewis structure

formal charge = V-L-B/2

V = the original valence electrons the atom had

L = the # of nonbonding valence electrons (# dots)

B/2 = # of bonding electrons /2 (# lines)

bond dipole

separation of charge within a covalent bond due to differences in EN between bonded atoms

dipole moment (overall or net dipole)

typically refers to the overall → points to more EN atom direction of charge separation (the sum of the bond dipole vectors)

sigma bonds

the first bond formed between two atoms by “head-on” overlapping orbitals (all single bonds are sigma bonds)

pi bonds

additional bonds formed between atoms by “lateral” overlapping orbitals