Test - don't know Flashcards
Explain how the line emission spectrum of hydrogen arises and provides evidence for the existence of energy level.
- In the ground state the hydrogen electron occupies the lowest available energy level.
- The electron can jump to a higher energy level if it receives a certain amount of energy.
- The excited state is unstable and electrons therefore fall back to a lower level.
- Energy is emitted as photon thus giving rise to a spectrum.
State what a beta particle is and give two examples.
Beta particles are electrons emitted from the nucleus of an atom.
- Negatively charged
- A greater penetrating power than alpha particles.
Give one way of detecting the presence of detecting cathode rays in a vacuum tube.
A shadow cast by the cross.
Three of the five fundamental processes that occur in mass spectrometry are detection, acceleration and vaporisation of substance. What are the other two fundamental processes that occur in mass spectrometry?
- Ionisation to form positive ions
- Seperation
What colour is observed in a flame test on a salt of (i) barium, (ii) lithium?
(i) Green
(ii) Crimson
Heisenberg’s uncertainty principle
This states that it is impossible to know both the position and the speed of an electron at the same time as electrons move in a wave motion.
Energy level
Is the discrete amount of energy an electron has when it is in an atom.
Energy sublevel
A group of atomic orbitals, within an atom, all of which have the same energy level.
Aufbau principle
Electrons occupy the lowest available energy level.
Hunds rule of maximum multiplicity
When two or more orbitals of equal energy are available, electrons fill them singly before filling them in pairs.
Pauli exclusion principle
No more than two electrons can occupy an orbital and this they can only do if they have opposite spin.
Explain how the expression E2-E1 = hf links the occurrence of the visible lines in the hydrogen spectrum to energy levels in a hydrogen atom.
- E2-E1 = The difference between a higher and lower level.
- f = frequency of line in spectrum.
- Each line produced is due to electrons falling from a particular higher level to a particular lower level.
Why do different electrons have unique atomic spectra?
As each element has a different distribution of energy levels giving rise to different electron transitions (jumps).
Name the instrumental technique that could have been used to confirm the identity of the product based on its absorption of a unique set of low energy electromagnetic radiations.
Infra red (IR)
State two limitation of Bohr’s theory that led to its modification.
- Didn’t work for higher electrons.
- Did not take wave-particle duality into account.
