Unit 1 - General Chemistry Review

atomic number (Z)

atomic number (Z)

# p+ (in neutral atoms)

mass number (A)

p⁺ + nº (in neutral atoms)

isotopes

atoms with same #p+ but different # nº

orbital e- capacity

2 e-

shell e- capacity

2n²

orbital shapes

S: spherical

P: dumbbell (3D)

ions

charged atoms

ionization energy

energy needed to remove e- from atoms in gaseous state

electron affinity

energy released after addition of e- to atom in gaseous state

• larger energy → stronger product

• groups 16 & 17 have highest EA

ionic bonding

metal transfers e- to nonmetal, both end up with noble gas configuration

polyatomic ions

charged molecules

covalent bonding

sharing of e- between anions to achieve full octet

exceptions (H, Be, B, P, S)

most stable bonding patterns

atom	H	C	N	O
# bonds	1	4	3	2
# lone pairs	0	0	1	2
total # e-	2	8	8	8

formal charge of atom

# Valence e^- - (unbonded e- + # bonds)

pos/neg formal charge of atom

• if atom has more bonds than that #, atom has + formal charge

• if atom has less bonds than that #, atom has - formal charge

VSEPR theory

e- in bonds and lone pairs repel producing 30º molecular shape

steps to predict VSEPR shapes

1. draw lewis structure

2. count # of e- regions on atom

3. use table

wedge dash system

• line bond: in plane of paper

• wedge bond: toward you

• dash bond: away from you/into the paper

orbital hybridization theory

shows that we can create hybrid orbitals (C-H bond is SP³ orbital)

sigma bond

created by bonds with at least one hybrid orbital

electronegativity

e- negatively affects ability of atom to pull e- density towards itself in a covalent bond (fluorine is most electronegative element)

polar bond

permanent bond dipole created by difference in electronegativity between atoms and asymmetric distribution of e- density (C-H is effectively non polar)

non polar bond

atoms are identical (a molecule can be non polar even if polar molecules are present)

ex: CF^4 (polar CF bonds cancel out)

electrostatic potential maps

show e- density distribution

• red: e- rich areas

• Blue: e- deficient area

• green: non polar area