Unit 1 Flashcards
(39 cards)
In what way does electromagnetic radiation have a dual nature?
Has a wavelength and frequency but also exhibits particle-like behaviour.
What is photon?
When electromagnetic radiation is absorbed or emitted by matter, it behaves more like a stream of particles than as a wave motion, these particles are called photons.
What happens when a photon is absorbed?
Electrons within the substance gain energy.
What happens when a photon is emitted?
Electrons within the substance lose energy.
What happens when energy is transferred to an atom?
Electrons can be promoted to higher energy levels.
How do electrons return to their original energy levels?
Energy must be lost from the atom.
In what form is energy lost from an atom?
As a photon.
How does atomic emmission spectra work?
Each line in an emission spectrum corresponds to the energy given out when an excited electron moves to a lower energy level.
What does atomic emission spectra provide evidence for?
Discrete (quantised) energy levels in atoms.
What are Atomic Emission Spectroscopy and Atomic Absorption Spectroscopy used for?
To identify and quantify the elements present in a sample.
How are electrons promoted for an atomic absorption spectra?
By absorbing radiation.
How is an absorption spectra produced?
By measuring how the transmission of light by the sample varies with wavelength.
How are electrons excited for an atomic emission spectra?
High temperatures are used.
What does the intensity of light emitted or absorbed represent in absorption and emission spectra?
The intensity of light is proportional to the concentration of the element present.
What are the four quantum numbers?
- N, which tells us which shell the electron is in
- L determines the shape of the sub-shell (s,p,d,f)
- M determines the orientation of the orbital
- S indicates the spin of an electron within an orbital
How many electrons can be held within a single orbital?
Two Electrons maximum.
What is the Aufbau Principle?
The Aufbau principle states that electrons fill orbitals in order of increasing energy, meaning the lowest energy sub-shells are filled first.
What are the order of orbitals in increasing energy?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p
What is meant by ‘Degenerate orbitals’?
Orbitals which have the same energy.
What is Hund’s rule?
Hund’s rule states that when degenerate orbitals are available, electrons fill each degenerate orbital singly and with parallel spins, before pairing up to fill the orbitals.
What is the Pauli Exclusion Principle?
The Pauli Exclusion Principle states that no two electrons in the one atom can have the same set of four quantum numbers.
What is the consequence of the Pauli Exclusion Principle?
No orbital can hold more than 2 electrons and the 2 electrons must have opposite spins.
What are the four blocks of the periodic table?
S block
P block
D block
F block
How can variation in the first and second Ionisation energies of the first 36 elements be explained?
In terms of relative stability of different electronic configurations.
