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Arrangement of Electrons in the Atom (Bohr theory 2 (Ground state…
Arrangement of Electrons in the Atom
Niels Bohr
Provided an insight into the arrangement of electrons in the atom
Bohr theory
Quantisation-electron in an atom can only have a fixed amount of energy(quantum)
Energy level-fixed energy value that an electron in an atom may have
Energy absorbed when electron jumps from n=1 to n=2
Energy emitted when electron falls from n=2 to n=1
Spectra
Carried out an experiment using hydrogen discharge tube-instead of seeing a continuous spectrum seen a series of narrow coloured lines
Light is emitted when an electric current is passed through hydrogen-emission line spectrum
Spread of colours is a continuous spectrum e.g rainbow
Each element has its own unique emission line spectrum
White light is passed through a glass prism light is broken up into an array of colours-spectrum
Bohr theory 2
Ground state-electrons occupy the lowest available energy levels
Excited state-electrons occupy higher energy levels than those available in the ground state
Provided energy by electricity or heating
specific amount of this energy is absorbed electrons jump from lower energy levels to higher ones
Unstable fall back to lower energy levels after a short time
Excess energy is released in the form of a photon of light has a definite amount of energy-light of a definite frequency
h-plancks constant
f-frequency of light emitted
Energy diff is proportional to the frequency of light emitted
Note
Spectrometer-instruments used to carry out experiments on spectra
Spectroscope-instruments used to observe spectra
Flame test
Using a damp wooden splint hold a sample of salt in the blue flame of a bunsen burner
Lithium-Crimson
Potassium-Lilac
Barium-Green
Strontium-Red
Copper-Blue-green
Sodium-Yellow
Bohrs theory 3
equation tells us that the energy difference is proportional to he frequency of the light emitted
Different numbers & type of electron transitions for each element. Give rise to a different emission line spectrum for each element
Series
n=1 Lyman series
n=2 Balmer series
n=3 Paschen series