chem 101 review: wave particle duality of light and...
TRANSCRIPT
Visible light is a form of electromagnetic radiation
Chem 101 Review: Wave Particle duality of light and matter
c = nl E = hnEnergy of one photon = E = hn = hc/l
Wave properties Particle properties
Matter has wave properties (De Broglie)
l = h / mv
c=speed of light (m/s)E = energy (J)λ = wavelength (m)h = Plank’s constant (s-1)v = frequency (s-1)
Δx • Δ(mv) ≥ h / 4π
Δx = uncertainty in position (m)Δ(mv) = uncertainty in momentum (kgms-1)h =Plank’s constant (s-1)
4π = 4π
λ = wavelength (m)h = Plank’s constant (s-1)m = mass (kg)v = velocity (m/s)
The exact momentum and mass of a particle cannot be known
Electrons exist as a probability function
Chem 101 Review: Shape of orbitalsName Quantum
numberMeaning Allowed values
principal quantum number
n size 1,2,3,4…
angular momentum quantum number
ℓ shape 0,1,2,3..(n-1)0=s 1=p 2=d 3=f
magnetic quantum number
mℓ orientation – ℓ…0.. + ℓ
spin quantum number
ms spin +1/2,-1/2
isoelectronic species :same number of electronsions with same charge:
Periodic trends in Ionic Radii
Summary:
easy to form negative ions
easy to form positive ions
smallest atoms
largest atoms
Zeff= Z-SZeff= effective nuclear chargeZ= number of protonsS= shielding (ca number of core electrons)
Lewis structures
Chem 101 5
1. Find the total number of valence electrons (account for any charges) = TOTAL
2. decide connection between atoms, draw a line to represent 1 electron pair for each connection, count the electrons SHARED
3. calculate the remaining electrons = TOTAL – SHARED, assign these to the terminal atoms to make octet (or 2 for H atom)
4. any electrons left? – put them on the central atom
5. if central atom doesn’t have an octet, make multiple bonds from nonbondedelectron pairs on terminal atoms
Choose central atom correctly
least electronegative atom(not H)
oxygen rarely bonds to itself
PCl3
For PCl3: 5 (for P) + (3 × 7) (for Cl3) = 26
26 – 6 = 20
3 bonds= 6
formal charge = number of valence electrons – total assigned electrons
Ionic bonding strength
dQQEel
21
Enthalpy of reaction
CH4 + Cl2 CH3Cl + HCl
Electronegativity and Molecular Polarity
Dipoles are a vector quantity
overall dipole moment
= 0
increases with increasing chargeIncreases with decreasing ionic radius
Resonance has impact on bond lengths and strengths
7
compare NO+, NO2- and NO3
-
N O
N OO-
N OO-
N-O bond order = 1.5
N-O bond order = 1.3
N-O bond order = 3
Increase in strength and decrease in length
[ ]+
Metals, insulators and semiconductors n -typep -type - dopant has more valence electrons than the host
- adds electrons to the conduction band
- e.g. P into Si
- dopant has fewer valence electrons than the host- leads to holes in the valence band
- e.g. B into Si
Doped semiconductors
Molecular Orbital Theory
Bond order =
½ {no. bonding electrons –no. antibonding electrons}Metallic Bonding
Intermolecular forces: a summary
interacting molecules or ions
are ions involved?
are polar molecules and ions
both present?
are polar molecules involved?
are H atoms bonded to N, O or
F atoms?A) ionic bondinge.g. NH4NO3
YES
NO
B) ion-dipole forcese.g. NaCl in H2O
YES NO
E) dispersion forcesonly (induced dipoles)
e.g. Ar(l), I2(s)
D) dipole-dipole forces
e.g. H2S, CH2Cl2
C) hydrogen bondinge.g. H2O, NH3, HF
YES
NO
NO
YES
van der Waals forcesA > B > C > D > E
Bonding in solidsMolecular Solids
Consist of atoms or molecules held together by intermolecular forces (iebenzene). Covalent-Network Solids
Consist of atoms held together, in large networks or chains, with covalent bonds (egdiamond, graphite).
Ionic Solids
Consist of ions held together by ionic bonds (i.e. by electrostatic forces of attraction) (eg NaCl, CaO). Metallic Solids
Consist entirely of metal atoms: electron sea
Intermolecular forces
Polar covalent bond (strong)
intermolecular attraction (weak)
Dipole-Dipole Interactions
Hydrogen bonding
London Dispersion Forces
δ– δ+δ– δ+
Temporary dipole
Cycloalkanes - general formula:CnH2n
Alkenes - general formula: CnH2n
cistrans
HNO3
H2SO4
H2OH2O
Br2
FeBr3
HBrHBr
Carboxylic acids
Chem 101 15
produced by oxidation of alcohols
CH3CH2CH2OH + [O] CH3CH2CH
O
+ H2O CH3CH2C
O
OH
[O]
Esters formed by condensation reaction between alcohols and carboxylic acids
Amides prepared by reaction of carboxylic acid with amine
H+/OH-
condensation rxn.
amides undergo hydrolysis
+ [O]