Unit 5: periodicity (1) Flashcards
- ppt 1 + ppt 2 + ppt 3a
Spectroscopy?
- Uses light to study matter
- Matter absorbs and releases light, and a spectroscope can provide information about structure of matter
Light travels as…?
Light can travel as particules and waves
How does light travels as waves?
- Light travels through space as electromagnetic energy (EM)
- Electromagnetic spectrum includes all types of EM energy such as radio waves, gamma rays, visible light…
Wavelenght?
- Lambda
- Distance between 2 peaks of troughs in a wave (m)
Frequency?
- V (nu)
- Number of waves that pass a given point in space per second
Amplitude?
Maximum height of a wave measured from it’s center. Affects intensity of light.
How do wavelenghts and frequencies are proportionnal?
They are inversely proportional!
If wavelenght increases, frequency decreases!
Propreties of radio waves?
They have long wavelenghts and low frequencies
Propreties of gamma rays?
They have short wavelenghts and high frequencies
Relationship between wavelenght and frequency?
Multiplied together, they give the speed of a wave, which is the c, constant speed of light (3.00 x 10*8 m/s)
Diffraction?
Bending of light around an object
Interference?
When light waves interact with each other and the amplitude of the resulting waves either increase of decrease
Photoelectric effect?
Phenomenon in which electrons are released from the surface of a metal when light strikes it.
What is the role of the threshold?
Light has to hit this threshold in order to emit electrons
Different lights on the photoelectric effect?
Red light = did not eject electrons (lowest energy)
Green light = did emit electrons at energy (higher energy)
Blue light = caused electrons to be emitted with highest energy (highest energy)
Max Planck?
He concluded that the energy lost or gained occured only in whole number multiples
h = 6.626 x 10*-34 (Planck’s constant)
Delta E = n x h x v
What did Einstein propose?
He proposed that light consists of particules called photons
Energy of a photon is equal to a single quantum
Ephoton = hv OR = hc/lambda
Broglie equation?
Lambda = h/mv
Continuous spectrum?
When light passes through a prism and separates into all the wavelenghts of visible light (from red to violet)
Line spectrum?
Series of discrete lines of light emitted by exciting atoms (ex: hydrogen gas)
The Bohr model?
- Electrons occupy discrete energy levels
- Energy levels of an atom, or orbits, are quantized
- Specific orbits correspond to specific amount of energy
Heinsenberg uncertainty principle?
- You can only predict the probable distribution of electrons
- The more certain you are about where an electron is, the less certain you are about where it is going.
- The more certain you are about where it is going, the less you are about where it is.
Quantum mechanical model of atom?
- Describes how electrons are arranged in an atom
- Quantum number is a set of 4 parameters that describe atomic orbitals, where an electron is likely to be found
- n, l ml and ms
Principal quantum number? (n)
- Shell
- Describes size and energy level of an orbital
- Has a positive integer: 1,2,3…
- As the n increases, energy increases and average distance of the electron from the nucleus increases.
Angular-momentum quantum number? (l)
- Subshell
- Defines 3D shape of an orbital
- l = n - 1 (l can be 0)
Exemples of l?
- l = 0 = s orbital (sphere)
- l = 1 = p (princpal)
- l = 2 = d (diffuse)
- l = 3 = f (fundamental)
- l = 4 = g
- l = 5 = h
Magnetic quantum number (ml)?
- Defines the spatial organisation of an orbital, or how many possible shapes there are
- From - l to + l with 2(l) + 1 possibilities
Spin quantum number (ms)?
- Differentiates each electron in an atom because moving electrons result in a tiny magnetic fiels
- (-1/2) and (+1/2)
Pauli Exclusion principle?
No 2 electrons in an atom cannot have the same four quantum numbers!
