Chem Test 2 Flashcards
oxidation number
the charge an atom would have if e- were completely transferred (like in an ionic compound)- book keeping method to track electrons
Rules for oxidation numbers
- in elemental form (Cl2, O2, Na)- O.N=0
- for monoatomic ions- O.N= ion charge
- sum of O.N for atoms in a compound- O.N=0
- sum of O.N for atoms in a polyatomic ion- O.N=ion charge
- Group 1A Alkali Metal- O.N=+1
- Group 2A Alkaline Earth Metals- O.N=+2
- Hydrogen-O.N= +1 (w/ nonmetals)
- Fluorine- O.N= -1
- Oxygen- O.N= -2
- Group 7A Halogens-O.N= -1 (except w/ more EN)
bond length
some distance attracts balance repulsion, is about the sum of atomic radii
bond energy and length
max attraction and min repulsion is the best distance
shortest bond= ___
triple, most energy to break
longest bond= ____
single, least energy to break
polar covalent bond
not equal sharing of e-, greater e- density around one atom
E.N.D
electronegativity difference, ability to hold e-
END= 0
nonpolar, pure covalent
END 0<2
polar covalent
END > 2
ionic
formal charge
difference btwn # of valence e- in an isolated atom and the # of e- assigned to that atom in a Lewis Structure; “charge an atom would have if all e- were equally shared”
Formal charge formula
FC=VE – NBE – 1/2BE
resonance structure
one of 2+ lewis structures for a single molecule that cannot be represented w/ 1 structure
bond order
of bonds
delocalized
electrons can move, they are spread out over space, represented by —–
incomplete octet
exception to octet rule, need valence e- to form octet, ex. BeH2
odd e- molecules
exception to octet rule, use formal charges to dictate which is best, ex. NO
expanded octet
exception to octet rule, principal quantum # n>2 (n=3+), ex. SF6
VSEPR
valence shell electron pair repulsion. Minimize repulsions each group of electrons are located as far as possible from the other e-
2 groups
180, linear
3 groups
120, trigonal planar
4 groups
109.5, tetrahedral
5 groups
90 and 120, trigonal bipyramidal
6 groups
90, octahedral
factors that affect bond angle:
2 lone pairs>lone pair & bonding pair> 2 bonding pair
bond angle
angle formed by the nuclei of 2 surrounding atoms with the central atom nucleus
valence bond theory
- a covalent bond forms when the orbitals of 2 atoms overlap and a pair of electrons occupy the overlap region
- depends on orbital shape and direction
- the greater the overlap, the stronger the bond
hybridization
the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory
way of correcting bond angles
linear hybrid
sp
trigonal planar hybrid
sp2
tetrahedral hybrid
sp3
trigonal bipyramidal
sp3d
octahedral
sp3d2
sigma
orbital overlap end to end; ALL SINGLE BONDS