Unit 1 Flashcards
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.
What is the arrangement of electron pairs in a molecule when there are two bonding pairs?
Linear
What is the arrangement of electron pairs in a molecule when there are three bonding pairs?
Trigonal Planar
What is the arrangement of electron pairs in a molecule when there are four bonding pairs?
Tetrahedral
What is the arrangement of electron pairs in a molecule when there are three bonding pairs and one lone pair?
Imperfect Tetrahedral
What is the arrangement of electron pairs in a molecule when there are two bonding pairs and two lone pairs?
Imperfect Tetrahedral
What is the arrangement of electron pairs in a molecule when there are five bonding pairs?
Trigonal Bi-pyramidal
What is the arrangement of electron pairs in a molecule when there are six bonding pairs?
Octahedral
How are the d-block transition metals described?
The d-block transition metals are metals with an incomplete sub-shell in at least one of their ions.
Which two transition metals are exceptions to the Aufbau principle?
Chromium and Copper.
How do transition metals lose electrons to form ions?
They lose the 4s electrons before the 3d electrons.
When is an element said to be in a particular oxidation state?
When it has a specific oxidation number.
What are the rules of oxidation numbers?
- The oxidation number of an uncombined element is 0.
- For ions containing single atoms (e.g Na+ or O2-) the oxidation number is the same as the charge on the ion.
- In most compounds, oxygen has oxidation number -2.
- In most compounds, hydrogen has oxidation number +1.
- Fluorine has oxidation number -1 in all its compounds.
-The sum of all oxidation numbers in a molecule or
neutral compound must add up to 0.
-The sum of all oxidation numbers in a poly-atomic ion must add up to the charge of the ion.
What is Oxidation?
Oxidation is an increase in oxidation number.
What is Reduction?
Reduction is a decrease in oxidation number.
What makes a compound an oxidising agent?
Compounds containing metals in high oxidation states tend to be oxidising agents.
