Flashcards in Electomagnetic Radiation And Atomic Spectra Deck (151):
What is radiation ?
what is its wavelength and frequency
It has a high frequency and short wavelength.
What is frequency measured in ?
Hz or s-1
What is wavelength measured in ?
M or nm
How do you turn m into nm
Divide by 1x10-9
What is speed of light ?
List all equations
E=lhc where v is wave number and v =1/wavelength
What is Avogadro (l) measured in ?
How do you change joules to kilojoules
Divide by 1000
What is the difference between emission and absorption spectra ?
What is the more common term for convergence limit ?
Absorption spectra is the visible colours spectrum and it has thick black lines
Whereas the emission spectra is a black background with coloured lines.
How is an emission spectra formed ?
To form an emission spectra an electron must be promoted from a low energy level to a higher energy level. This can be done by applying heat or electrical energy. Then the electron falls back down to the lower energy level by emitting energy in the form of photons. Draw diagram. Each line in the diagram represents radiation of a specific wavelength or frequency and from these the difference in energy can be calculated.
What is an orbital ?
It is a region of space where there is a high probability of finding an electron.
What are principal quantum numbers ?
They are used to label the energy levels.
The higher the principal quatum number the further away the level is from the nucleus represented by n
What are s orbitals
They are Spherical in shape and can hold 2 electrons
What are p orbitals
They are dumbbell shape and have 3 types X , y and z. They can hold a maximum of 6 electrons and are degenerate .
What does degenerate mean ?
They have the same energy
What are d orbitals ?
They can hold 10 electrons as there are 5 d orbitals. They are also degenerate.
What's the 3 rules about filling orbitals
Paul's exclusion principle
What is paulis exclusion principle
This states that an orbital cannot contain more than 2 electrons and they must have opposite spins.
This states that when electrons are placed into orbitals they must fill energy levels up from low energy to higher energy for example 1s will be filled before 2s.
Hunds rule ?
This states that when there is degenerate orbitals the electrons must fill each one singly with parallel spins before pairing.
What's the 2 anomalies in electron configuration why does it occur ?
Copper and chromium
Copper 1s2 2s2 2p6 3s2 3p6 4s1 3D10
Chromium is 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Before wouldn't be stable arrangement
Are electrons removed from 4s or 3d first and why ?
4s as it has a lower energy
What has the highest ionisation energy and why ?
Noble gases as they have a complete p orbital in outer energy level which is stable
Why does be have higher ionisation tan boron
Draw orbital boxes and relies that be has full 2s orbital where as b has not full 2p
Be has higher ionisation energy as you are removing electrons from a full more stable 2s orbital so you need more energy compared b which is removing electrons from a not full 2p orbital which is less stable so requires less energy.
Why does nitrogen have higher ionisation than oxygen
Draw orbital box and realise that nitrogen has Half filled 2p while oxygen has full first 2p
Higher ionisation of nitrogen as it has a half filled 2p orbital which I'd more stable so requires more energy to remove electrons compared to oxygen Whig has a full first 2p orbital which results in repulsion making it easier to remove electrons.
What's the 2 types of electron pairs you can get
Bonding pair and lone pair
How do you prEdict the shape of a molecule. ?
Calculate the number of bonding pairs and lone pairs in the molecule , then use chart that's memorised to find shape
What shape is it if there's 2 bonding pairs
Bond angles of trigonal planar ?
Bond angles of tetrahedral ?
3 bonding 1 lone
Bond angle pyramidal
2 bonding 2 lone
Bond angle in bent
5 bonding pairs
3 bonding 2 lone
5 bonding 1 lone
4 bonding 2 lone
When comparing ch4 ( 109.5) and nh3 (107) why difference in bond angle
Ch4 is larger the nh3 bond angle . This is because nh3 has a lone pair of electrons which causes most repulsion compared to the other bonding pairs.
What is angular momentum quantum number ?
Relates to the type of orbital represented by l
Magnetic quantum number ?
This is the orientation if the orbitals represented by m
Spin quantum number
This related to the spin of an orbital so either +1/2 or -1/2 represented by s
What is a dative covalent bond ?
When an atom provides both electrons in a covalent bond
What does an oxidation number indicate ?
The number of electrons lost, gained or shared as a result of chemical bonding.
How do you work out the oxidation. State for single atoms ?
Same as charge , look at the valency .
Oxidation number for compound ?
Set up algebraic equation to work out charge , must equal charge of ion
What is reduction in terms of oxidation number ?
oxidation number decreases
What is oxidation in terms of oxidation number ?
If oxidation number increases
What is a reducing agent ?
Always oxidized , lose electrons
What is oxidising agent
Electrons are gained as it is reduced
Where are the best reducing agents ?
Where are the best oxidising agents ?
The bottom left
What is a resonance structure ?
When there’s more than one equivalent form for one structure
What is a complex ?
Usually a positive central metal ion surrounded by Ligands
What are ligands ?
particles that are able to donate electrons in order to form a dative covalent bond.
This could be through lone pairs ie water and ammonia or having a negative charge
What’s the name of ligands that donate one pair of electrons ?
Monodentate is water and ammonia
What is a bidentate ligand
A ligand that donates 2 electron pairs but they must be on different parts of the molecule
Name other ligand classifications
What is a coordination number ?
The number of bonds of the Central ion.
How do you work out the coordination number ?
Count round central ion
Chloride ion ?
Oxide ion ?
Cyanide ion ?
Oxalate ion ?
Carbon monoxide ?
How do you name ligand ?
Prefix for ligand , name of ligand
If negative ligands then add ate for Latin names.
If vanadium is negative
If chromium is negative
How do you name complex ?
In square brackets
Name ligand first with prefix first
Oxidation state of metal
Why are some complex ions coloured ?
The ion absorbs light in certain parts of the visible spectrum.
The remaining wavelengths are transmitted
The colour seen is the complimentary colour to the colour absorbed
Why do transition metals or ions absorb light ?
Due to d-d orbital splitting. In a transition metal or ion the five d orbitals are degenerate. The ligands surrounding the central ion will affect the energy of the d orbitals.
The ligands will donate their electrons into the d orbitals that lie on the axis this causes the d orbitals to rise in energy while the other orbitals are unaffected. Transition metals absorb light because photons excite the lower d orbitals up to a higher energy levels.
What affects the splitting of the d orbitals ?
The nature of the ligands
What is a heterogeneous catalyst
A catalyst that is in a different state to the reactants
What is a homogeneous catalyst
A catalyst that is in the same state as the reactants
What occurs during adsorption
Molecules of one or both of the reactants forms bonds with the catalyst and this weakens the bonds within the molecule
What occurs during reaction
The molecules react on the catalyst surface, the angle of collision is more likely to be favourable as one of the molecules is fixed.
What occurs during desorption
The reactant molecules leave the catalyst and the active site becomes vacant ready for another reactants molecule.
What is the definition of equilibrium?
When the rate of the forward reaction is equal to the rate of the backwards reaction. The concentration of the products and reactants constant but not equal.
What is the equilibrium constant shown by ?
What is the expression for K
What is the units of K
In K what is value of 1
Pure liquids and solids such as water
WHat does a high value of k ( above 1) tell you about the reaction?
That there is a higher percentage of products in the equilibrium
What does it tell you about the reaction if k is 1
Equilibrium lies neither to the left or the right , similar amounts of products and reactants
K is smaller than 1
Higher percentage of reactants in reactants in the equilibrium
What is partial pressure ?
The pressure exerted by gas when it is alone in a space of volume
Does a catalyst effect the equilibrium?
No it does not therefor it doesn't alter the value of K
What is the only thing that alters the value of k ?
What is the ionic product of water ?
When there's an equal number of 0H ions to h ions represented by Kw
What effect does increasing the temperature have on the ionic product of water Kw
It increases it and increases the dissociation
What is the formula for nitric acid ??
What is a strong acid
An acid that dissociates completely in a solution
List strong acids
What is a weak acid
An acid that dissociated partially in a solution
List weak acids
All carboxylic acids
What is a weak base
It is a base that doesn't dissociate completely in a solution
Give an example of a weak base
What is a strong base
A base that dissociates completely in a solution
Give example strong base
All exempt ammonium hydroxide ie lithium hydroxide , potassium hydroxide
What is the base and acid if an acidic salt ?
Strong acid and weak base
What is the base and avid of an alkaline salt ?
Strong base and weak acid
What is base and acid of neutral salt ?
Strong acid and base
What is an acid
What is an. Alkali
What do you call a substance that acts as an acid and a base
What is a conjugate base ?
Whatever is left of the acid ( negative)
What is a conjugate acid ?
Whatever if left of the base after it accepts a hydrogen ( positive )
What is a buffer solution ?
It's a solution which the pH remains approximately constant even when small amounts of acids and bases are added to the solution
What's in an acidic buffer ?
Strong base , weak acid and salt of weak acid
What is an alkaline buffer ?
Weak base , strong acid and salt if weak base
Why are indicators used ?
They are used in acid base titrTions as they change colour at the end point.
What are indicators usually ?
Weak acids that are different in colour to the conjugate base
What is standard enthalpy of formation ?
When a compound is formed from its elements in their usual room temperature state
What is standard temperature in kelvins
What is entropy ?
It's the amount of disorder in a system
What's the entropy of a perfect crystal and why ?
Zero as there is no motion at all
What has happened to the entropy of a reaction if the s is negative
What has happened to the entropy of a reaction if the s is positive
What is a spontaneous or feasible reaction ?
A reaction that proceeds towards the products rather than the reactants
How is a reaction feasible in terms of total entropy ?
The total entropy must be positive .
How is a reaction feasible in terms of Gibbs energy
Must be negative
What do you need to do in Gibbs
Change standard entropy change (s) must be divided by 1000 so kjk.
What the units of Gibbs
If 2 positive in Gibbs what temp will make feasible
If 2 negative in Gibbs what temp will make it feasible
How do you work out temperature of feasible reaction
Sub Gibbs is o into equation t = h over s
What if Gibbs in reversible reaction
What is unit of rate equation
What is zero order
When changing concentration of one of the reactants has no effect in the rate of the reaction
What is first order
When doubling the concentration doubles the rate or tripling the concentration triples the rate
What is second order
When doubling the concentration quadruples the rate
Units of 1st order.
S-1 or min-1
Units 2nd order
Mol-1ls-1 or mol-1lmin-1
Units 3rd order
Mil-2l2s-1 or moo-2l2min
What is the slowest step in a reaction
The rate determining step