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.
Name applications for the use of knowledg of energy levels in everyday life
atomic absorbtion spectrometry (AAS) - identify dangerous elements in water
fireworks
Descibe limitations of Bohrs theory
- He didn’t take into account wave particle duality
2.The excact position and velocity of an electron could not be measured at the same time so they cannot discribes as ravelling in fixed paths- Heisenberg’s uncertainty principle - Didn’t take into account sub levels
what is a sub level
subdivision of a main energy that consists of one or more atomic orbitals of equal energy
what is heisenberg’s uncertainty principle
it impossible to measue simultaneously both the exact position and velocity of an electron
what is an atomic orbital
region in space around the nucleus of an atom where there is high probality of finding an electron
List energy sub level from1-4
4f
4d
4p
3d
4s
3p
3s
2p
2s
1s
Who devised a equation to work out the probiotic of finding an electron in a particular sublevel
Erwin Schrödinger
Describe a S sub level
Spherical and each contain 1 orbital
Describe a P sub level
Dumbbell shaped
Conduits of three orbitals (Px ,Py, Pz)
Describe D sub level
They contain 5 orbitals
How many electrons does each orbital hold
2
What is wave particle dualitiy
All moving electrons actually move in a wave motion
give two differences between an atomic orbit, as describes by bohr, and an atomic orbital
Orbit - electrons travel in fixed paths in a definite location
-has a max capacity of 2n2(squared) electrons
Orbital region of space where there is a high probability of finding an electron
has a max capacity of 2 electrons
Distinguish between a 2p orbital and a 2p sublevel
2p orbital has a max capacity of 2 electrons
2p sublevel has a max capacity of 6 electrons, consists of three 2p orbitals
