Electronic configurations - the electromagnetic spectrum and emission spectra Flashcards
What is the electromagnetic spectrum?
A range of frequencies that covers all electromagnetic radiation and their respective wavelengths and energy. It shows the relationship between frequency, wavelength and energy.
What is a continuous spectrum?
Contains light of all wavelengths. Appears as a continuous series of colours.
What is a line spectrum?
Two types: emission and absorption
Each element has its own characteristic line spectrum.
Can be used to identify the element.
What happens if an electron’s energy is increased?
They can jump to a higher energy level.
What happens when electrons returns to their original energy levels?
The emit energy in a mixture of different frequencies
What is an emission spectrum?
Series of coloured lines against a dark background.
Tells us the light emitted can only be certain frequencies - it is quantised.
Produced by light emitted when a pure gaseous element is subjected to a high voltage under reduced pressure.
What is an absorption spectrum?
Made when a cold gas is placed between the prism and a source of visible light of all wavelengths.
Dark lines / gaps in the continuous colour show the wavelengths absorbed by the gas.
What is the relationship between energy and wavelength?
E ∝ 1/λ
Energy of the radiation is inversely proportional to the wavelength.
What speed do electromagnetic waves all travel at?
The speed of light, C
3.00 x 10^8ms^-1 (in data booklet)
wavelength & frequency formula
c = f x λ
c = speed of light
f = frequency
λ = wavelength
What does quantization mean?
Each line in the emission spectrum of an element has a specific wavelength, which corresponds to a specific amount of energy.
Electromagnetic radiation comes in discrete quanta.
What is a photon?
A quantum of energy, proportional to the frequency of the radiation
Photon & frequency of radiation formula
E = h x f
E = specific energy possessed by the photon, in joules (J)
h = Planck’s constant (6.63 = 10^-34 Js)
f = frequency of the radiation, in hertz (Hz) or inverse seconds (s^-1)
What is Bohr’s theory for the model of the hydrogen atom based on its emission spectra?
- electrons can conly exist in stationary orbits around the nucleus, which are associated with discrete energy levels
- when an electron with the lowest energy level absorbs a photon of the right amount of energy, it moves to a higher energy level and stays for a short time
- when the electron returns to a lower energy level, it emits a photon of light. The photon represents the energy difference between the two levels
What are the states of hydrogen (energy levels)?
ground state: n=1 - lowest possible energy
exited states: n=2, 3, … - unstable atoms
excited states spontaneously return to ground state by emitting photons of specific wavelengths
What are the rules for energy between states?
Electrons will absorb or release only the exact energy that is required to move between allowable energy states.
Any excess will not be absorbed.
If an insufficient amount of energy is supplied the electrons will not move.
What is convergence?
Allowable energy levels get closer together when the electron moves further away from the nucleus.
The line emission of hydrogen is evidence for the existence of this.
What are the regions and amount of energy for the energy jumps in the hydrogen spectrum?
Jumps, Region, Energy, respectively
n∞→ n3, Infrared, Low
n∞ → n2, Visible, ↓
n∞ → n1, Ultraviolet, High
