Title: Electromagnetic Spectrum radiation with both electric and magnetic components
1Electromagnetic Spectrumradiation with both
electric and magnetic components
2Electromagnetic Radiation
- Electromagnetic wave
- wavelength
- frequency
- amplitude
3Wavelength Frequency Amplitude
4Plancks Quantum Theory
- E hn hc/l
- where nl c
- E ? energy
- h ? Planck's constant
- n ? frequency
- c ? speed of light
- l ? wavelength
5Photoelectric Effect
- the emission of electrons by substances, such as
metals, when light falls on their surfaces.
6Photoelectric Effect
7a quantum, unit, of electromagnetic energyLine
Spectrum
Photons
- spectrum emitted by a luminous gas or vapor
- appears as distinct lines characteristic of the
various elements present
8Emission Spectrum
- spectrum of bright lines, bands, or continuous
radiation - characteristic of a specific emitting substance
9Line Emission Spectrum
10Energy Transitions
- Ground State - lowest energy state for electrons
in an atom - Excited State - any energy state above the ground
state
11Absorption Spectrum
- light shinning on a sample causes electrons to be
excited from the ground state to an excited state - wavelengths of that energy are removed from
transmitted spectra
12Bohr Model for the Hydrogen Atom
- E -B/n2
- E (-2.179 ? 10-18 J/part.)
- (6.022 ? 1023 part./mole)
- (1 kJ/103 J)/n2
- (-1312 kJ/mol)(1/n2)
- where n ? quantum number
- 1, 2, 3, 4, 5, 6, 7, etc
13Bohr Model
- for hydrogen
- ground state n 1
- excited state n gt 1
-
14Hydrogen Spectrum
- E (-2.179 ? 10-18 J)(1/ni2 - 1/nf2)
- where ni initial state quantum number
- nf final state quantum number
15Hydrogen Spectrum
16Line Spectra
- Lyman series ? ultraviolet
- n gt 1 ? n 1
- Balmer series ? visible light
- n gt 2 ? n 2
- Paschen series ? infrared
- n gt 3 ? n 3
17Quantum Mechanics
- Heissenberg Uncertainty Principle - it is
impossible to know precisely both the location
and momentum of an electron
18Orbitals
- region of probability of finding an electron
around the nucleus - 4 types ? s p d f
- maximum of 2 electrons per orbital
19Pure Atomic Orbitals
- shape of orbitals / energy level
- s spherical 1
- p dumbbell 3
- d complex 5
- f very complex 7
20Atomic Orbitals
21Quantum Numbers
22Quantum Numbers
- n ? energy level
- (1, 2, 3, 4, 5, 6, 7, etc.)
- l ? type of orbital
- (s l0 p l1 d l2 f l3)
- ml ? which orbital
- (one value per orbital -l ? -l1 ? 0 ? l-1 ? l)
- s ? direction of spin
- (-1/2 or 1/2)
23Electrons
24Electronic Configurationand the Periodic Table
25Electronic Configurations
- The shorthand representation of the occupancy of
the energy levels (shells and subshells) of an
atom by electrons.
26Electronic Configuration
- H atom 1 electron 1s1
- He atom 2 electrons 1s2
- Li atom 3 electrons 1s2, 2s1
- Cl atom 17 electrons
- 1s2, 2s2, 2p6, 3s2, 3p5
27Electronic Configuration
- As atom
- 33 electons
- 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3
- or
- Ar 4s2, 3d10, 4p3
28Electronic Configuration
- negative ions
- add electron(s), 1 electron for each negative
charge - S-2 ion
- (16 2)electrons
- 1s2, 2s2, 2p6, 3s2, 3p6
29Electronic Configuration
- positive ions
- remove electron(s), 1 electron for each positive
charge - Mg2 ion
- (12-2)electrons
- 1s2, 2s2, 2p6
30Lewis Electron Dot Structures
31Trends in thePeriodic Table
- atomic radius
- ionic radius
- ionization energy
- electron affinity
32Atomic Radius
- decrease left to right across a period
- as nuclear charge increases, number of electrons
increase however, the nucleus acts as a unit
charge while the electrons act independently,
pulling electrons towards the nucleus, decreasing
size
33Atomic Radius
- increase top to bottom down a group
- each additional electron shell shields the
outer electrons from the nuclear charge - Zeff Z - S
- where Zeff ? effective nuclear charge
- Z ? nuclear charge, atomic number
- S ? shielding constant
34Atomic Radius
- increases from upper right corner to the lower
left corner
35Atomic Radius ofMain Group Elements
36Atomic Radius ofs-, p-, and d- Block Elements
37Nuclear Magnetic Resonance
http//mrsec.wisc.edu/edetc/NMR/index.html
The most common nuclei studied using NMR are
H-1, C-13, F-19 and P-31. Most MRI studies
involve the H-1 nuclei in water. When these
nuclei are exposed to an external magnetic
field, their spins can be parallel or
anti-parallel to this external field.
38Ionic Radius
- same trends as for atomic radius
- positive ions smaller than atom
- negative ions larger than atom
39Ionic Radius
- Isoelectronic Series
- series of negative ions, noble gas atom, and
positive ions with the same electronic
configuration - size decreases as positive charge of the
nucleus increases
40Isoelectronic Series
41Sizes of Ions and their Neutral Atoms
42Ionization Energy
- energy necessary to remove an electron to form a
positive ion - low value for metals, electrons easily removed
- high value for non-metals, electrons difficult to
remove - increases from lower left corner of periodic
table to the upper right corner
43Ionization Energies
- first ionization energy
- energy to remove first electron from an atom
- second ionization energy
- energy to remove second electron from a 1 ion
- etc.
44First Ionization Energies
45Electron Affinity
- energy released when an electron is added to an
atom - same trends as ionization energy, increases from
lower left corner to the upper right corner - metals have low EA
- nonmetals have high EA
46Electron Affinities