CHM135 LECTURE NOTES
Structure can be studied by looking at spectroscopy: the interaction between matter and
electromagnetic radiation.
Electromagnetic radiation is a form of energy thought of as waves traveling through space. It
travels through a vacuum at the speed of light.
Wave characteristics
1. Wavelength (λ) units: m (1 nm = 10-9 m)
2. Frequency (v, nu): number of waves per second that pass through a set point, units: s-1,
Hz
3. Amplitude (A): height of wave; classically related to energy (intensity) of light
There is an inverse relationship between wavelength and frequency on the electromagnetic
wave spectrum.
Waves interfere
- Constructive waves are formed when peaks combine with peaks and troughs combine
with troughs (waves in phase)
- Destructive waves are formed when peaks combine with troughs (waves out of phase)
E.g. diffraction of waves. Where the peaks align, a high intensity band is produced.
Light does have many wave properties but it does not behave as a classical wave. Instead it is
composed of particles of energy known as photons.
1. To eject an electron from the metal, a minimum intensity of light is needed.
2. Above this minimum, the KE of the ejected electron increases with light frequency.
3. Above this minimum, increased light intensity increases the number of ejected electrons,
which increases the current.
Shorter wavelength = higher frequency = higher energy
Ephoton = E binding + E KE
E KE = Ephoton - E binding
Ephoton = hf = hc/λ
Question: A laser pointer emits 4.0mW of light at 532
nm. How many photons of light are emitted in one
minute? (1.00 W is 1.00 J/s)
E tot = (4.0/1000) x 60 = 0.24J
,Ephoton = (6.626x10-34 J·s) (3.0x108 ms-1) / 532nm = 3.7364662x10-19J
E tot = E photon x n photon
n photon = E tot / E photo
n photon = 0.24J / 3.7364662x10-19J = 6.4231813x1017 photons
Matter: discrete particles with determinate mass and position
The double slit experiment:
- Particles will pass through the slit and accumulate to form distinct peaks
- Waves diffract
- Electrons diffract (nickel crystal experiment shown below)
H2 → 2H
● Passage of electricity through gas of atoms causes
atoms to emit light.
● Only four frequencies were observed in the visible part
of the spectrum.
● These observed frequencies are different for excited
atoms of different elements.
● Another element will produce discrete lines, but the
position of these lines differs across the elements.
,Before 1900
- Light: wave character - e.g. wavelength, frequency, diffraction
- Matter: particulate character - e.g. mass and position
Experiments involving photoelectric effect, diffraction by electrons and atomic line spectra led to
the discovery of wave-particle duality:
- Light: both wave and particulate character
- Matter: both wave and particulate character (larger objects do not have observable wave
character)
3 quantum numbers describing the orbital
1. Principal quantum number (n) → size of the orbital; determines energy of electron
2. Angular momentum quantum number (ℓ) → shape of the orbital
3. Magnetic quantum number (mℓ or m) → orientation of the orbital
4. Electron spin quantum number (ms or s) → ms = -½ or +½
Orbitals: max 2 electrons; must have opposing spin
1. Size of orbital: n = 1, 2, 3…
2. Shape of orbital: ℓ = 0, 1 …, n-1
3. Orientation of orbital: m = -ℓ, -ℓ+1… ℓ-1, ℓ
, n ℓ Notation m/mℓ Number of
orbitals
1 0 1s 0 1
2 0 2s 0 1
2 1 2p -1, 0, +1 3
3 0 3s 0 1
3 1 3p -1, 0, +1 3
3 2 3d -2, -1, 0, +1, +2 5
4 0 4s 0 1
4 1 4p -1, 0, +1 3
4 2 4d -2, -1, 0, +1, +2 5
4 3 4f -3, -2, -1, 0, +1, 7
+2, +3
Structure can be studied by looking at spectroscopy: the interaction between matter and
electromagnetic radiation.
Electromagnetic radiation is a form of energy thought of as waves traveling through space. It
travels through a vacuum at the speed of light.
Wave characteristics
1. Wavelength (λ) units: m (1 nm = 10-9 m)
2. Frequency (v, nu): number of waves per second that pass through a set point, units: s-1,
Hz
3. Amplitude (A): height of wave; classically related to energy (intensity) of light
There is an inverse relationship between wavelength and frequency on the electromagnetic
wave spectrum.
Waves interfere
- Constructive waves are formed when peaks combine with peaks and troughs combine
with troughs (waves in phase)
- Destructive waves are formed when peaks combine with troughs (waves out of phase)
E.g. diffraction of waves. Where the peaks align, a high intensity band is produced.
Light does have many wave properties but it does not behave as a classical wave. Instead it is
composed of particles of energy known as photons.
1. To eject an electron from the metal, a minimum intensity of light is needed.
2. Above this minimum, the KE of the ejected electron increases with light frequency.
3. Above this minimum, increased light intensity increases the number of ejected electrons,
which increases the current.
Shorter wavelength = higher frequency = higher energy
Ephoton = E binding + E KE
E KE = Ephoton - E binding
Ephoton = hf = hc/λ
Question: A laser pointer emits 4.0mW of light at 532
nm. How many photons of light are emitted in one
minute? (1.00 W is 1.00 J/s)
E tot = (4.0/1000) x 60 = 0.24J
,Ephoton = (6.626x10-34 J·s) (3.0x108 ms-1) / 532nm = 3.7364662x10-19J
E tot = E photon x n photon
n photon = E tot / E photo
n photon = 0.24J / 3.7364662x10-19J = 6.4231813x1017 photons
Matter: discrete particles with determinate mass and position
The double slit experiment:
- Particles will pass through the slit and accumulate to form distinct peaks
- Waves diffract
- Electrons diffract (nickel crystal experiment shown below)
H2 → 2H
● Passage of electricity through gas of atoms causes
atoms to emit light.
● Only four frequencies were observed in the visible part
of the spectrum.
● These observed frequencies are different for excited
atoms of different elements.
● Another element will produce discrete lines, but the
position of these lines differs across the elements.
,Before 1900
- Light: wave character - e.g. wavelength, frequency, diffraction
- Matter: particulate character - e.g. mass and position
Experiments involving photoelectric effect, diffraction by electrons and atomic line spectra led to
the discovery of wave-particle duality:
- Light: both wave and particulate character
- Matter: both wave and particulate character (larger objects do not have observable wave
character)
3 quantum numbers describing the orbital
1. Principal quantum number (n) → size of the orbital; determines energy of electron
2. Angular momentum quantum number (ℓ) → shape of the orbital
3. Magnetic quantum number (mℓ or m) → orientation of the orbital
4. Electron spin quantum number (ms or s) → ms = -½ or +½
Orbitals: max 2 electrons; must have opposing spin
1. Size of orbital: n = 1, 2, 3…
2. Shape of orbital: ℓ = 0, 1 …, n-1
3. Orientation of orbital: m = -ℓ, -ℓ+1… ℓ-1, ℓ
, n ℓ Notation m/mℓ Number of
orbitals
1 0 1s 0 1
2 0 2s 0 1
2 1 2p -1, 0, +1 3
3 0 3s 0 1
3 1 3p -1, 0, +1 3
3 2 3d -2, -1, 0, +1, +2 5
4 0 4s 0 1
4 1 4p -1, 0, +1 3
4 2 4d -2, -1, 0, +1, +2 5
4 3 4f -3, -2, -1, 0, +1, 7
+2, +3
