Bohr's Theory Flashcards
Who proposed the existence of energy levels/ shells/ orbits
Bohr
define energy level
the fixted amount of energy an electron in an atom has
why cannot electrons occupy spaces between energy levels
it is unstable and will fall to a lower energy level
ground state
when all the electrons in an energy level occupy the lowesy avliable energy levels, most stable state for an electron
excited state
when electrons have absorbed enough energy to jump/ promoted to higher energy levels- unstable state, electrons will drop back down to lover levels
what is the evidence for the existance of energy levels in atoms
line emission spectrum for hydrogen
give two ways electrons in an atom can be excited
heating the element
passing an electric current though the element
what is a line emission spectrum
a series of coloured lines that correspond to specific frequencies of light emitted when when electrons in an element are excited
Explain how the visible line emission spectrum of hydrogenarises and provised evidence for the existence of energy levels
-In the ground state of hydrogen atoms, its electrons occupy the lowest energy level, N=1
-if electrons absorb sufficent energy, they are promoted/ jump up to higher energy levels.
-electrons in the excited state are tempoary and they are unstable and fall back dowb to lower energy levels a short amount of time.
-A definite frequency photon of frequency is emitted depending of electron transition.
-electrons that transition back to n=2 produce a frequency that gives visible coloured light.
This relationship can be demostrated by.
E2-E1 = hf (f= photon)
what name is given to the series of visible coloured lines produced in a hydogen emission spectrum, caused by electrons falling from higher energy levels to n=2
Balmer series
explain why there is no yellow line in the hydrogen emission spectrum.
There is no corresponding electron transition in hydrogen that would produce light frequency that gives a yellow colour.
Describe the flame test
Fume cupboard
Concentrated Hydrochloric acid
Platinum wire
If wire is clean there should be no colour produced
Crush salt with Pestle and mortar
Identify the metal from the salt
Why do different metals produce different flame colours
Each element has a different electron configuration
Therefore different electron transitions are possible
So different frequencies of light will be emitted from each element
Lithium Chloride produces the colour
Crimson Red
Potassium Chloride produces the colour
Lilac
Barium Chloride produces the colour
Green
Strontium Chloride produces the colour
Dark red
Copper Chloride produces the colour
Blue/green
Sodium Chloride produces the colour
Yellow
What are flame tests
heating an elemnt in a busen burner will cause that element to produce a charateristic colour. The element can therefor be identified
Give two reasons why different elements have different atomic emission spectra/impart
different colours to a bunsen flame
Different metals have different transitions between their energy levels
Different metals have different numbers of electrons…
meaning specific freauencies of light are emitted for each specific element
What does AAS stand for
Atomic absorbtion spectrometry
What is AAS
When white light is passed through a gaseous sample of an element, certain wavelengths were missing.
These lines correspond excatly to the lines produced in produced in the emission line spectrum
Name uses for mass specrometry
identifying dangerous element in water (presence of hard metals)
identifyong elements present in stars.
