CHEM Ex 2

CHEM 1030, Priya Matthew

ionic compounds

• metal-nonmetal bond

• electrostatic attraction between cation & anion

lattice energy

energy released when ionic solids form

empirical formulas

lowest whole # ratio of atoms

Coulomb’s law

shows lattice energy depends on ion charge and size

(formula)

Ag⁺, Zn²⁺, Cd²⁺

known transition metal charges

Hg₂ ²⁺, O₂ ^2-

unsimplified cations

anhydrous

no water present

hydrated

when water is present

covalent compound

• nonmetal-nonmetal bond

• sharing of e^- pair

molecular fornmula

gives ACTUAL numbers of atoms in a molecule

empirical formula

gives RELATIVE numbers of atoms in a molecule

• (lowest whole number ratio)

covalent bonds & hydrates

when prefixes are used

molecular mass (MW)

sum of masses of all elements in a compound

electronegativity

increases from left → right

increases up^ from a group

polar bonds

unequal sharing of e^- in a bond

• due to electronegativity differences

isomerism

same molecular formula with different arrangement of atoms

4 bonds, 0 lone pairs

Carbon’s bonding (C)

3 bonds, 1 lone pair

Nitrogen’s bonding (N)

2 bonds, 2 lone pairs

Oxygen’s bonding (O₂)

1 bond, 3 lone pairs

Halogens bonding (if no octet expansion)

valence e^- — (sticks + dots) or (bonds + lone pairs)

Formula Charge equation

resonance forms (hybrid)

structures w/ the same arrangement of atoms, but dif. arrangement of bonds & lone pairs

B, Al, Be

electron-deficient atoms (2 w/ 3 bonds, 1 w/ 2 bonds)

free radicals (img, ch. 5)

odd-electron molecule with an unpaired e^- in its structure

bond energy

avg. energy required to break a covalent bond

bond energy increases as

• bond length decreases

• multiple bonds form

trend in bond energy

VSEPR Theory

shape minimizes e^- pair repulsion

• i.e. e^- groups are as far apart as possible

steric number (SN)

number of lone pairs + atoms bonded to central atom

• a double bound = ONE e^- group

1. Find e^- geometry (e.g.)

2. Find MG by considering only atoms (not lone pairs)

how to find Molecular Geometry (MG)

linear → trigonal planar → tetrahedral → trigonal bipyramidal → octahedral

e.g. order from SN: 2 → 6

(img) how to draw tetra, trig bi, octa, + angles

make these flashcards (flip)

compression (img)

lone pairs distort bond angles due to ___

trigonal planar → bent (img)

trigonal planar M.G. (decreasing)

tetrahedral → trigonal pyramidal → bent (img)

tetrahedral M.G. (decreasing)

trigonal bipyramidal → seesaw → T-shaped → linear (img)

trigonal bipyramidal M.G. (decreasing)

octahedral → square pyramidal → square planar → T-shaped → linear (img)

octahedral M.G. (decreasing)

1. Any polar bonds?

2. Electron Geometry (e.g.)?

3. Do dipoles cancel due to shape?

steps to predict polarity