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Chemistry - Bohr’s Theory Flashcards Part 2

Chemistry38 CardsCreated 4 months ago

This deck covers key concepts from Bohr's theory, including energy levels, atomic emission spectra, and the limitations of Bohr's model. It also explores related topics like flame tests, atomic orbitals, and wave-particle duality.

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Who proposed the existence of energy levels/ shells/ orbits?

Bohr
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Key Terms

Term
Definition
Who proposed the existence of energy levels/ shells/ orbits?
Bohr
Define energy level.
The fixed 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 lowest available 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 lower levels.
What is the evidence for the existence of energy levels in atoms?
Line emission spectrum for hydrogen.
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Chemistry - Bohr’s Theory Flashcards Part 2
TermDefinition
Who proposed the existence of energy levels/ shells/ orbits?
Bohr
Define energy level.
The fixed 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 lowest available 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 lower levels.
What is the evidence for the existence 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 through the element.
What is a line emission spectrum?
A series of coloured lines that correspond to specific frequencies of light emitted when electrons in an element are excited.
Explain how the visible line emission spectrum of hydrogen arises and provides 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 sufficient energy, they are promoted/jump up to higher energy levels. -Electrons in the excited state are temporary and they are unstable and fall back down to lower energy levels a short amount of time. -A definite frequency photon of frequency is emitted depending on electron transition. -Electrons that transition back to n=2 produce a frequency that gives visible coloured light. This relationship can be demonstrated by E2-E1 = hf (f= photon).
What name is given to the series of visible coloured lines produced in a hydrogen 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 element in a Bunsen burner will cause that element to produce a characteristic colour. The element can therefore 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 frequencies of light are emitted for each specific element.
What does AAS stand for?
Atomic absorption spectrometry
What is AAS?
When white light is passed through a gaseous sample of an element, certain wavelengths were missing. These lines correspond exactly to the lines produced in the emission line spectrum.
Name uses for mass spectrometry.
Identifying dangerous elements in water (presence of hard metals), identifying elements present in stars.
Name applications for the use of knowledge of energy levels in everyday life.
Atomic absorption spectrometry (AAS) - identify dangerous elements in water, fireworks.
Describe limitations of Bohr's theory.
1. He didn’t take into account wave-particle duality. 2. The exact position and velocity of an electron could not be measured at the same time so they cannot be described as traveling in fixed paths - Heisenberg's uncertainty principle. 3. Didn’t take into account sublevels.
What is a sublevel?
Subdivision of a main energy that consists of one or more atomic orbitals of equal energy.
What is Heisenberg's uncertainty principle?
It is impossible to measure 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 probability of finding an electron.
List energy sublevels from 1-4.
4f, 4d, 4p, 3d, 4s, 3p, 3s, 2p, 2s, 1s
Who devised an equation to work out the probability of finding an electron in a particular sublevel?
Erwin Schrödinger
Describe a S sublevel.
Spherical and each contain 1 orbital.
Describe a P sublevel.
Dumbbell shaped, consists of three orbitals (Px, Py, Pz).
Describe D sublevel.
They contain 5 orbitals.
How many electrons does each orbital hold?
2
What is wave-particle duality?
All moving electrons actually move in a wave motion.
Give two differences between an atomic orbit, as described by Bohr, and an atomic orbital.
Orbit - electrons travel in fixed paths in a definite location, has a max capacity of 2n² 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.