Part 1 - Introduction to d and f element chemistry Flashcards
(88 cards)
1
Q
basic periodic table facts
A
- elements are listed in order of atomic number (i.e. number of nuclear protons)
- periods refer to the rows
- groups refer to the columns
- divided into four blocks: s block, p block, d block, f block
2
Q
d-block elements
A
- groups 3 to 12
- known as transition metals
- divided into 3d, 4d, 5d, and 6d metals
- all are naturally occurring except for Tc. this element is highly radioactive
- usually find d-block elements as oxides and sulfides in nature
- oxides are preferred for the light and early transition metals
- sulfides are preferred for the heavy and late transition metals
3
Q
post-transitional elements
A
- refers to group 12
- they cannot be considered as transition metals because their d-shell is full in the 0 and 2 oxidation states. usually transition metals are partially filled in their most common oxidation states
- has distinct enough properties
4
Q
f-block elements
A
- divided into lanthanoids and actinoids
- lanthanoids are 4f elements while actinoids are 5f elements
- in lanthanoids, all are naturally occurring except for Pm, while only Th and U are naturally occurring in actinoids
5
Q
early transition metals
A
groups 3 to 7 in the periodic table
6
Q
late transition metals
A
groups 8 to 11 in the periodic table
7
Q
light transition metals
A
first row of d-block, also known as the 3d elements in the periodic table
8
Q
heavy transition metals
A
second and third row of d-block, also known as the 4d and 5d elements in the periodic table
9
Q
creation of elements
A
initially, all matter and energy were concentrated at a single point. then, the Big Bang occurred, which lead to the formation of subatomic particles. these subatomic particles formed the lightest element, hydrogen. over time, fusion and related processes within stars allows for other natural elements to be produced. they are released when the star decays explosivley
10
Q
nuclear forces
A
- two types: short and strong
- they compensate for the repelling of protons in the nucleus, and hold together the protons within
- these forces are only significant at short distances. at some point, there are too many protons and the nuclear forces are no longer effective
11
Q
stability and occurrence of actinoids
A
- only Th and U are natural
- U is the heaviest natural element
- all the other actinoids are the products of nuclear reactions, have short lifetimes, and do not accumulate
12
Q
iron production
A
- overall reaction: 2 C + O2 –> 2 CO
Fe2O3 + 3 CO –> 2 Fe + 3 CO2 - carbon is introduced into the top of the furnace with limited amount of air being introduced at the bottom, allowing the formation of carbon monoxide due to the incomplete combustion of carbon dioxide
- carbon monoxide will be useful for this process because it is good at reducing metal oxides
- Fe2O3 is introduced into the top of the furnace, while heat is applied to the bottom of the furnace to create the temperature gradient in which the gradual production of iron will occur
- Fe2O3 will travel down the furnace, where CO reduces it to Fe3O4 at around 500C, then to FeO at 700C, and then to Fe at 1000C
- CaO is used to bring down melting temperature of metal oxides. it reacts with SiO2 to form slag, which is easily removed
- sources: ore provides iron oxide, coke provides carbon, limestone provides CaO
13
Q
applications of d-block metals
A
- structural materials: construction, medicine
- materials with useful physical properties: electrical conductors, permanent magnets, Li-ion batteries, superconductors, piezoelectric materials, ruby laser
- catalysis: haber-bosch process, H2SO4 production, Pt/Rh catalysts in cars, Pt/Rh/Pd catalysts for organic reactions, Ti/Zr polymerization catalysts
- medicine: Pt anticancer drugs, Tc imaging, Au arthritis drugs
14
Q
how do lanthanoids usually exist?
A
- they usually exist as phosphates
- monazite, LnPO4, which contains small amounts of Th
- bastenite, LnCO3F, which contains mainly the earliest lanthanoids
15
Q
recovery process of lanthanoids
A
1) Monazite is subject to treatment with sodium hydroxide
2) the precipitated oxide is then treated with acid, leaving the Th oxide behind as a solid [ThO2]
16
Q
why was it hard to find lanthanoids as pure substances?
A
the lanthanoid III ions have similar chemical properties, making them difficult to separate
17
Q
lanthanoid separation
A
- ion exchange chromatography
- EDTA is used since it has a strong affinity for lanthanoids
- EDTA will form a stable complex with the lanthanoids: [Ln(EDTA)]-
- there will be equilibrium between Ln3+ and [Ln(EDTA)]- complex
- the smaller the lanthanoid ion, the stronger the binding will be to EDTA
- more strongly-binded cations will elute first because it can pass through the column quickly
- very slow process, inefficient, expensive
18
Q
2014 Nobel prize in physics
A
- lanthanoid application
- developed blue LEDs
- lead to the creation of red and green LEDs
- more importantly, it lead to the creation of white LEDs. blue light and phosphorus emitting yellow were mixed for us to get what appears as white
- can be used for displays
19
Q
magnetic properties of lanthanoids
A
- these magnetic properties exist because of the several unpaired electrons in the valence shell of lanthanoids
- permanent magnet generator and tower magnet in wind turbine use Nd. wind turbines would only be possible with this lanthanoid
- using lanthanoids in wind turbines takes up a lot of energy because the lanthanoids must be purified first
20
Q
rare earths production/lanthanoid production
A
- china is the world’s main producer of lanthanoids
- because of tensions between china and the west, the west are always trying to look for new ways to produce lanthanoids
21
Q
occurrence and recovery of uranium
A
- U is found as U3O8 (i.e. pitchblende), and can be extracted by treatment with acid: U3O8 + H2SO4 –> [UO2]SO4
- UO2 is uraninite
- uranium has many impurities as a result of the decay processes. its many isotopes are unstable and subjective to radioactive decaying processes. when the isotopes decay, they get transformed into other elements, resulting in the impurities present in uranium
- uranium can be separated from other impurities by ion exchange
- uranium is recovered from aqueous solutions as U3O8 (i.e. yellow cake)
22
Q
3 types of radioactive decay processes
A
alpha radiation, beta radiation, gamma radiation
23
Q
alpha radiation/alpha particle
A
- attracted towards negative electrode, indicating the presence of positive charged particles
- mass number of 4, charge of +2
- therefore, when an element is undergoing alpha radiation or emitting an alpha particle, it’s mass number will decrease by 4. since the substance looses 2 positive particles, it will become the element that has an atomic number 2 less than the starting element
24
Q
beta radiation/beta particles
A
- opposite of alpha particles
- attracted toward positive electrode, indication the presence of negative charged particles
- beta particles emit electrons but these electrons come from when the nuclei split into a proton and electron
- since the nuclei splits, the atomic number will increase by 1. the atomic mass stays the same.
25
gamma particles
these particles are neutral
26
uranium enrichment
- uranium is used in nuclear power generation
- includes U-235 and U-238. they only differ in the number of their neutrons
- because of the splitting that occurs in U-235, the concentration of this isotope needs to be increased. the most common enrichment method is the centrifuge process
27
what happens when U-235 absorbs a neutron?
when U-235 atom absorbs a neutron, it looses stability, causing nuclear fission (i.e. it splits into two nuclei). the nuclear power generation utilizes the thermal energy emitted at this time. this process emits 2 neutrons. the neutrons emitted from this fission process can be used to multiply the neutrons
28
what happens when U-238 absorbs a neutron?
when U-238 atom absorbs a neutron, it does not split. however, U-238 changes into plutonium 239
29
uranium enrichment process
1) heat is used to get rid of nitrate, and obtain the form of NO2: [UO2](NO3)2 --> UO3 + NO + NO2 + O2
2) UO3 is reduced to UO2: UO3 +H2 --> UO2 + H2O
3) UO2 + 4HF --> UF4 + 2H2O
4) UF4 + F2 --> UF6. this product is used for enrichment
- UF6 is a volatile material
- centrifugation or semipermeable membranes can be used to separate the 235-UF6 and 238-UF8 isotopes
30
thermal diffusion
- uses the transfer of heat across a thin liquid or gas to accomplish isotope separation
- exploits the fact that the lighter 235-U gas molecules will diffuse toward the hot surface, while the heavier 238-U gas molecules will diffuse toward a cold surface
- process abandoned for gaseous diffusion
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electromagnetic isotope separation process (EMIS)
- electromagnetic separation process
- metallic uranium is vaporized and then ionized to positively charged ions
- these ions are accelerated and deflected by magnetic fields on to their respective target
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gaseous diffusion
- technology used to produced enriched uranium by forcing UF6 through semi-permeable membranes
- produces slight separation between molecules containing 235-U and 238-U
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different uranium enrichment processes
thermal diffusion, electromagnetic isotope separation process, gaseous diffusion, centrifuge enrichment process
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centrifuge enrichment process
- modern process
- rotor spins at extremely high speeds in the centrifuge
- this powerful centrifuge force causes the UF6 gas to be pushed toward the rotor walls
- at this time, UF6 with a higher proportion of 238-U is pushed outward, while UF6 with a higher proportion of 235-U tends to gather around the center
- UF6 gas in the centre is collected and processed into enriched uranium
- inefficient. has to be done multiple times and at once
35
solution of Schrodinger equation
- wave function
- ¥ = radial function*angular function
- depends on 3 quantum numbers: n, l, ml
- this solution is not unique. rather, it belongs to a family of solutions that can be distinguished and are reliant on the 3 quantum numbers
- this solution is only possible for hydrogen-like atoms. there is no possible analytical solutions for atoms/ions with more than one electron
36
radial wave function
depends on distance from electron to the nucleus
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angular wave function
depends on angles that specify position of electrons
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energy of hydrogen-type orbital
- En = - (h*c*R*Z^2)/n^2
- depends only on n
- En is zero when n = infinity, i.e. when the electron is removed from the atom
- the lower the energy, the more lightly bound the electron is
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quantum number
n, l, ml, ms
40
n
- principal quantum number
- labels the shell, defines orbital size and energy
- n = 1, 2, 3...
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l
- orbital angular momentum quantum number
- defines orbital type and its orbital angular momentum
- l = 0 (s-shell), = 1 (p-shell), = 2 (d-shell), = 3 (f-shell)...
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ml
- orbital magnetic quantum number
- defines the orientation of an orbital and the value of its orbital magnetic moment around the field axis
- ml = -1, ...., 0, ....,1
43
ms
- spin magnetic quantum number
- defines the orientation of the electron spin with respect to the external magnetic and determines the value of the spin magnetic moment around the field axis
- ms = +1/2 or -1/2, i.e. up or down
- can be considered as a quantum number although the wave function of a hydrogen-like atom does not depend on it because when the electron is near the external magnetic field, it leads to 2 states of energy
44
what prevents the collapse of the atom?
the kinetic energy of the electron
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boundary surface
- region of the space within which there is a certain probability of finding the electron
- integrated probability can be used to define this
46
Heinsberg uncertainty principle
cannot know the momentum and position of a particle at the same time
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radial node
radial wavelength is 0
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radial nodes of s-orbitals
- 1s has 0 radial nodes
- 2s has 1 radial node
- 3s has 2 radial nodes
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radial nodes of p-orbtials
- 2p has no radial nodes
- 3p has 1 radial node
- 4p has 2 radial nodes
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nodal planes
- position of nodal plane tells us direction/sign of orbitals
- plane in which there is zero electron density
- s-orbitals have no nodal planes
- p-orbitals have 1 nodal plane
- d-orbtials have 2 nodal planes
- f-orbitals have 3 nodal places
51
electron configuration
- statement of the mono electronic wavefunctions (orbitals) used to build a multielectronic function
- when we say that an electron "occupies a certain orbital" we mean that its state is associated to this particular approximate wavefunction
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polyelectronic atoms
- more than one electron
| - their wavefunctions are built by combinations of monoelectronic functions (i.e. orbitals)
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penetration
extent to which an electron can approach the nucleus
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shielding
reduction of true nuclear charge (Z) to the effective nuclear charge (Zeff)
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effective nuclear charge
- a correction factor is applied to the true nuclear charge
| - it is the charge that an electron feels
56
screening
electron-electron repulsions can effectively screen a positive nuclear charge. low screening results in the orbital having low energy
57
comparing 2s and 2p orbitals
- in hydrogen-like atoms, 2s and 2p orbitals have the same energy
- penetration of 2s electrons through the inner 1s shell is larger than for 2p electrons
- because the penetration of 2s electrons is larger, this means they are screened less and thus have lower energy
- the lack of degeneracy between these two orbitals is due to interelectron repulsions
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size of orbitals from largest to smallest
ns, np, nd, nf
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why do some orbitals overlap?
- the space between quantum numbers is not constant, resulting in the overlapping of orbitals
- from the bottom: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d, 4f
60
building-up (aufbau) principle
- as Z increases, ns and np orbitals smoothly decrease in energy because these penetrating orbitals experience a steadily increasing nuclear charge
- the 3d orbitals have a constant energy region up to Z = 18[Ar] because they do not effectively penetrate the Ar core, resulting in sustained shielding from the increasing nuclear charge by the inner ns and np orbitals
- after Ar, 3d orbitals start to experience the nuclear charge, resulting in a sharp drop in energy. electrons here can enter the 4s or 3d orbitals as they have comparable orbital penetration
61
electron configuration of transition metal cations in complexes
- (n-1)d^m ns^0, where m is the number of valence electrons left
- all valence electrons are in (n-1)d orbital. there are no electrons in ns orbitals
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two types of atomic radii
metallic radii, covalent radii
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ionic radii
- add the two radii's together
| - we have to take one ion as a standard. the radii depends on this arbitrary reference
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relationship between atomic/ionic radii and coordination number
- the higher the coordination number, the larger the radius
- this makes sense because when there are a lot of atoms close together to the one we're studying, we will have more steric hinderance, thus increasing the radius.
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coordination number
number of closest atoms
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general trends in the atomic radii
- size increases sharply at the start of each period due to very low Zeff
- for the alkali metals, size increases with atomic number as the valence electrons are located further from the nucleus
- for the second and third periods, size decreases as Zeff increases
67
atomic radii of d-block elements
- size decreases across the transition metals due to increasing Zeff
- exceptions: Mn, Cu & Zn, Pd & Ag & Cd, Au & Hg
- first row of TMs are smaller than 2nd and 3rd row
- 2nd and 3rd row TMs are approximately the same size with similar properties and chemistry. this is because the 3rd row of TMs are smaller than expected due to lanthanoid contraction
68
radii of lanthanoids
2 main features:
1) decrease in the atomic radii and cationic radii known as the lanthanoid contraction
2) unusual behaviour in the atomic radii of Eu and Yb. they are much higher than the rest
69
ionization energy (IE)
- energy required to remove an electron from a gas-phase atom
- IE correlates with atomic radius (i.e. large radius = low ie)
- 1st IE's increase across a period and up the group
- for TMs, IE increases across the series
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successive IEs
these energies tend to increase, but there is no clear patter down the group
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electron affinity (EA)
- energy released (Absorbed) upon the gain of an electron by a gas-phase atom
- no simple trend with multiple exceptions
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electronegativity (EN)
- the power of an atom to attract electrons towards itself in a bond
- general trend: EN increases across the period and up the group
- 3 different scales/ways to define EN: Pauling, Mulliken, Allred and Rochow
73
Pauling
- created a way in which EN can be defined
- ∆X = XA - XB = (∆D)^1/2, where ∆D is the energy of the A-B bond in eV
- relative scale
- requires a standard
74
Mulliken
- X = 1/2(IE+EA)
- proposed that EN can be calculated by determining the average of IE and EA
- not used today
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Allred and rochow
- EN is determined by the electrical field on the surface of the atom (i.e. Zeff)
- X = 0.744 + (35.90*Zeff)/r^@
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EN range of lanthanides
1.1-1.3
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EN range of actinides
1.3-1.5
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reaction with O2
- most d- and f-block metals react with O2 to form oxides (exception: noble metals)
- passivation: effect in which the oxide layer that has formed on these metals protect the metals from further oxidation
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reaction with water
- in the absence of O2 and at ph of 7, d- and f-block metals do not react with water
- exceptions: Y, Sc, La. they yield hydroxides and H2
- when d- and f-block metals give hydrated cations in water
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reaction with acids
- depends on the acid
| - noble metals do not react with most mineral acids
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reaction with H2
- some of the d- and f-block metals react with H2 at ambient or elevated temperatures to form hydrides
- hydrogenation is a standard technique used to produce fine metal powders
- saline hydrides, metallic hydrides
- ability of transition metals to form hydrides is explored for hydrogen storage
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saline hydrides
nonvolatile, electrically nonconductive, crystalline solids
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metallic hydrides
nonstoichiometric, electrically conductive solids
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standard reduction potential
deduces the stability and the reducing/oxidizing ability of a particular oxidation state
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frost diagram
- plot of NE˚ vs oxidation states
| - shows stability of elements at different oxidation states
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stable oxidation states
+3 for early and light transition metals, +2 for late and heavy transition metals (exception is Cu)
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oxidation states in 4d and 5d elements
higher oxidation states are more stable
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highest oxidation states: oxygen vs fluroine
oxygen is more effective than fluorine in bringing out the highest oxidation states
