Alkali metals (group 1)
Hydrogen has no color or smell,what more characterizes hydrogen?
-->Burns easily -->Has a high ionization energy (é close to nuclei) -->Has three natural isotopes that has large differences (hydrogen, deterium, tritium) -->Low melting and boiling point -->Do not solve good in any solvent -->Is only similar to metal in solid form -->Has the highest thermal conductivity of any gas (higher for para than ortho) värmeledningsförmåga! -->Present usually in H2 form which is not so reactive and has covalent bonds
Name how you can producue hydrogen
-->Electrolysis of water -->Strong acid with a hydrogen generating metal -->Metal hydrides (H-) with water -->Steam reforming (products called syngas --> CH4+H2O) -->Metals that form amphoteric hydroxides with hydroxide
Name the use of hydrogen
-->Production of ammonia (NH3) called Haber-bosch-process N2 + 3H2 --> 2NH3 -->Hydrocracking (breaking C-C bonds) -->Coolant in electrical generators -->Semiconductor industry; potential electron donor in oxide materials
What characterize the elements in group 1? standard enthalphy of hydration? metallic radius/melting/boiling? soluble?
-->They form an octet by donating an electron, which is also why they gladly form cations. -->They will not be found in the nature 'alone' as they react so easily - most of them are found in salts -->The standard enthalpy of hydration is very negative (increasing in the group) -->The second ionization energy is much higher than the first (due to octet) but will decrease in the group -->Compounds with alkali metals are soluble in water and form a basic solution also meaning they have negative reduction potential -->The metallic radius increase in the group -->Melting/boiling points decreases in the group -->As you go down in the group, they are more reactive
Salt hydrides: The molten compound conducts electricity and produce hydrogen gas at the anode when electrolysed in molten halides. Write down the reaction with hydrogen in molten metal
2 Me(l) + H2(g) → 2 MeH(s) Me(lI) + H2(g) → MeH2(s)
Write down the reactions with sodium and chlorine gas in the Down cell
2Na+ + 2é --> 2Na(l) 2Cl--> Cl2(g) + 2é Overall reaction: 2Na+ + 2Cl- --> 2Na(l) + Cl2(g)
Describe hydrates
A substance that has watermolecule(s) as a part of its structure. In some compounds, the water remains bound in it's form, while for some solids the hydrate water (crystalization water) can be dried off which will appear as a color change (common for chloride compounds with hydrate water)
What's an alkalide?
An alkalide is a chemical compound in which alkali metals are anions (negative charged). Known alkalides: sodide/natride, potasside/kalide, rubidide/caeside
What's antibonding orbital?
An antibonding orbital is a type of molecular orbital (MO) that weakens the bond between two atoms and helps to raise the energy of the molecule relative to the separated atoms.
Why are compounds with alkali metals soluble in water?
As they form ions with +1 charge which results in 'weak' crystals (not as strong crystals as the ions with higher charge)
Ammonia is another solvent group 1 metals can react to. Write down the reaction NH3 reacting with Na. What will form at high metal concentrations?
At high metal concentration, ion-clusters will form. Na+NH3→NaNH2 + H2 is an example. (you get salt and H2)
Water dissociates into H3O+ and OH-, what's the auto dissociation and Kw?
Auto dissociation: H2O + H2O --> OH- + H3O+ Kw = [OH-] * [H3O+], pH = -log[H3O+]
D2O is used as solvent for 1H and 13C NMR and as moderator in nuclear reactors. Why? And what more can D2O in polar ice tell us?
Because it doesn't give any signal and it absorbs neutrons (fast). D2O in polar ice can give us information on climatic changes
Why does hydrogen have a low melting and boiling point?
Because it has very weak intermolecular forces. The lack of intermolecular forces holding the molecules together means they will separate (melt and evaporate) very easily.
Why do group 2 have a higher melting/boiling point than group 1?
Because of more efficient metal bonds
Why does water have such a high boiling point (100) when it should be -100 theoretically?
Because water(in liquid form) forms intermolecular bonds which is really strong and they are called hydrogen bonds which is H bonding to F, O or N. Thanks to the electronegativity, the H atom wil bind to the free electron pair in another water molecule (the neighbouring) To prove hydrogen bonds, you need at least two molecules.
Boiling point, melting point and the enthalpy of vaporization is different for some compounds. Write down from the lowest to the highest in each category for NH3, HF, H2O and CH4
Boiling point/Enthalpy of vaporization: CH4 < NH3 < HF < H2O Melting point: CH4 < HF < NH3 < H2O
Describe agostic bonds
Bonds between C-H and transition metals.
What is good to know about H2O2? what is it called? is it toxic? what kind of agent is it?
Called hydrogen peroxide. It's poisonous, redox amphoteric and a bleaching agent
What's (poly)crystalline?
Composed of many microscopic crystals (grains) stuck together in different orientations
Alkali metals ozonides (MeO3), what's good to know about them? what type of agents? does all of the alkali metals form ozonides? Which is the most resistant compared to KO3/RbO3?
CsO3 is more resistant than KO3 and RbO3. Strong oxidising agents All of the alkali metals form ozonides
What can you use deuterium for? (common)
Deuterium lamps are used in photometry and UV-Vis spectrometry (and have high intesity ultraviolet radiation)
Why does the melting/boiling point decrease in the group?
Elements in the group one exhibit metallic bonding: the positive nuclei are held together thanks to the attraction to delocalised electrons. As the number of electron shells increases down the group, and consequently the atomic radii get bigger, the attraction between the nuclei and outer shell (valence) electrons decreases. Hence, the bonds are weaker and less energy is required to break them.
The formation of both ammonia and hydrides can appear by the reaction with hydrogen and what more? For ammonia: and for hydrides:
For ammonia: N2 and Fe/Ru as catalyst For hydrides: electropositive metals and non-metals
What's good to know about alkali metal salts? how are they formed? which bond do they have? soluble in polar solvents(water)? conduct electricity? melting point? are they any exceptions
Formed by the reaction of acid with base (neutralisation). Ionic bond between cations (element + "ion") and anions ("-ide") Are readily soluble in polar solvents (water) Have high melting points Conduct electricity when molten Form a low number of insoluble phases Exception: Li! with the solubility!!! low solubility in water, but soluble in ethanol, acetone and ethyl acetate
How's the gas hydrate a clathrate?
Gas hydrates has water as a 'host molecule' which surrounds the gas molecule aka guest molecule (can be liquid).
Name the analytical methods to analyte hydrogen: H2, H3O+, molecular compounds and isotopic compounds
H2: NMR, GC and FTIR H3O+: pH-electrode, titration Molecular compounds: NMR, FTIR, XRD, GC-MS Isotopic composition: radiometry, mass spectrometry
Name the most common H + O compounds
H3O+, H2O2, H2O and OH-
Explain the different requirements behind hydride formation
Heating Radical reaction Polarisation of the bond due to different electronegativity; • non-polar with B, C, Si, P • H negative with e-positive metals • H positive with F, O, N Frequently non-stoichiometric composition
Describe saline hydrides
Hydrogen act as a hydride ion and form compounds with metals from group 1&2
What's a hydride?
In chemistry, a hydride is the anion of hydrogen, H− or, more commonly, it is a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties.
What type of bond will group 1 most commonly form?
Ionic bonds. But, they can form covalent bonds too, lithium has highest covalent character and highest polarisability however we also have N2.
Describe clathrate(klatrat)
Is molecules/atoms sealed in cavities (håligheter) in bigger molecules.
Litium is quite rare. How is this element used?
It is used in batteries and drugs to treat bipolar diseases.
What's a chlor-alkali process? And describe the process with anode and cathode
It's an electrolysis of aqueous solution NaCl, the main source is of both Cl2(g) and NaOH. At the cathode: 2H2O(l) + 2é --> H2(g) + 2OH-(aq) At the anode: 2Cl-(l) + Cl2(g) + 2é Redox: 2H2O (l) + 2Cl- (aq) --> 2OH- (aq) + Cl2(g) + H2(g)
Alkali metals amides are insoluble in ammonia and the formation of amides with the alkali metals are not all reversible, which is reversible/irreversible?
K, Rb and Cs are reversible: é + NH3 --> NH2- + 1/2H2 Li and Na are irreversible: Na+ + é + NH3(l) --> NaNH2(s) + 1/2H2
Name the coordination numbers for each element and explain what's coordination number
Li: 4 Na, K: 4 but with different geometries Cs, Rb: 6, possible octahedron The coordination number (aka ligancy) of a central atom in a molecule/crystal is the number of atoms/molecules/ions (aka ligands) bonded to it.
Hydride like coordination compounds, give two examples. (used as reducing agents)
LiAlH4 and NaBH4
The solubility of alkali metals halides in water is given by the lattice energy and hydration energy. Which compound is least soluble?
LiF
Which alkali metal halides are insoluble in organic solvents that contain O?
LiF, LiBr, LiI and NaI
In the gas phase alkali halides form ion-pairs, with a certain contribution of covalent bonding, which alkali halide has the highest covalent bonding?
LiX
Strong interaction gives highest Kexc. Order down the magnitude of Kexc for group 1 from lowest to highest
Magnitude of Kexc Li+ < Na+ < K+ < Rb+ < Cs+
Transition metal hydrides have a large varation of structure and properties. Which bond? stoichiometric/non-stoichiometric?
Mainly covalent bonds Stoichiometric compounds but non-stoichiometric when direct reaction with hydrogen(mostly) No theory for the formation/properties of these hydrides except for UH3
Alkali metals form halides when coming into contact between the elements, write down the reaction
Me + 1/2 X2 --> MeX
As group 1 metals is very reactive to water (more reactive, as you go down the group!) except Li, there is a reaction template that is good to know. Write it down.
Me(s) + H2O --> Me+(aq) + 1/2 H2 + OH- (aq)
Oxides, peroxides and superoxides react with water (oxygen + metal). Write down the reactions
Me2O + H2O --> 2MeOH Me2O2 + 2H2O --> 2MeOH + H2O2 2MeO2 + 2H2O --> 2MeOH + H2O2 + O2
Which compounds with Na are common and is used in water treatment plants (vattenreningsverk)?
Na2CO3 and NaCl
All alkali metals burns in air (O2). Which metal pairs with oxides, peroxides or superoxides?
Oxides (O^2-): Li, Na Peroxides(O2^-2): Na (Li & K) Superoxies(O2-): K, Rb, Cs
What's good to know about the reaction with salt like hydrides? what does it react with? bases/acids? produces?
Produces metal and hydrogen gas React with water and in humid air (except LiH) Strong bases, can deprotonate weak acids Strong reducing agents
The metals form organometallic compounds which is important in organic synthesis (especially Li-organic compounds). Name the properties and describe what's organometallic compounds
Properties • react violently with oxygen and water • spontaneous ignition on air • sovalent properties: soluble in non-polar solvents, low melting points Organometallic compounds tend to act as carbon-based nucleophiles as well as bases. They have dipoles where the carbon is negative, common example is H3C-Li. Grignard reagents are made through the addition of Mgm6
Where can clathrates be found?
Seabed, ocean, deep lake sediments
The elements in group 1 are metals obviously(except hydrogen obviosly), what characterize metals?
Shiny, soft, good conductor of current(ström)/heat/electricity, malleable, ductile (smidbar/böjbar). The conducitivy will decrease with increasing temperature!
Which elements are the most common one in the group and why are they important?
Sodium (Na) and Potassium (K, kalium) which are important for biological processes.
At low temp. Cs and Rb form suboxides! What's suboxides?
Suboxides are a class of oxides wherein the electropositive element(that can be a metal, in this case Cs and Rb) is in excess relative to the ''normal'' oxides.
Explain the Aufbau principle
The Bohr model where electrons fill up the lowest available energy level before beginning to fill the next shell. Aufbau means builiding up in German so the principle is all about how the shells are filled with electrons (1s,2s,2p..and so on) depending on energy level.
What is the biggest difference between H2O and D2O?
The boiling/melting point is higher (for D2O) and D2O has a less dissociation (Kw at 298 K) by the factor 5
Free forms of alkali metals can form with a Down cell where different type of products are formed with the help of sodium and chlorine (gas). Briefly describe how the Down cell works
The electrolyte is NaCl that has been heated to the liquid state. Ca+ is added to reduce the temp. required to keep it liquid. The Na metal has an iron cathode and where the Cl2 vents are, there is a carbon anode. (easier to watch the pic)
How does the flame test work?
The energy in the flame is sufficient(tillräcklig) for exciting electrons in the alkali metals. Then emmited wavelenght will appear depending on the energy levels which is specific for each element. If you excite an atom or an ion by very strong heating, electrons can be promoted from their normal unexcited state into higher orbitals. As they fall back down to lower levels (either in one go or in several steps), energy is released as light. Each of these jumps involves a specific amount of energy being released as light energy, and each corresponds to a particular wavelength (or frequency). As a result of all these jumps, a spectrum of lines will be produced, some of which will be in the visible part of the spectrum. The colour you see will be a combination of all these individual colours. The exact sizes of the possible jumps in energy terms vary from one metal to another. That means that each different metal will have a different pattern of spectral lines, and so a different flame colour.
Explain what the standard enthalpy of hydration means
The energy that forms when the element reacts with a solvent
Explain Hund's rule
The rule says that in a given energy level, electrons will go into unoccupied orbitals first before filling orbitals that already have one electron. Example: if a shell has four orbitals that each hold 2 é, each orbital will get one é before any orbital will have two.
Agostic bonds are common in coordination compounds/complexes. Describe how
The two é involved in the C-H bond enter the empty d-orbital of a transition metal, resulting in a three-center two-electron bond
What's crown ethers? How is the nomenclature?
They are cyclic polyethers composed of ethyleneoxy-groups aka carbon compounds with a cyclic strucutre containing at least two oxygens Nomenclature: [number of atoms]-crown-[number of oxygen] Solvate the groups (1) ions, ion-dipole bond, the more oxygen, the stronger the bond and the oxygen is evenly distributed in the ring. The diameter of the ring must fit the ion. Polarising groups lower the binding force! Soluble in polar and non-polar media.
What's Grignard reagents?
They are made through the addition of Mg metal to alkyl or alkenyl halides (except F tho)
What's cryptands?
They are synthetic bi-and polycyclic multidentate ligands for a variety of cations (three dimension coverage). Additional N-atoms in the ring will coordinate the cation due to more electronegative sites. They are more stable with alkali metal than the crown ethers. Nomenclature: [number of O in each ring]cryptand. Example [2.2.2]cryptand
Describe covalent hydrides
When a hydrogen atom and one or more non-metals form compounds
Covalent hydrides can be natural/alkaline and acidic depending on which group the hydride will bind to. So, name each covalent hydride with each group(14-17) and if the soluion is base/acidic/neutral
XH4 (group 14) neutral, binary XH3 (group 15) weakly alkaline (base), binary XH2 (group 16) weakly acidic/amphoteric, binary HX (group 17) strong acids, binary
As the lattice energy and ionisation energy is decreasing in the group, what happens with ΔH0 to alkali metals halides if MeX and X = F and X = Cl, Br,I?
for X = F ΔH0 becomes less negative in the group for X = Cl, Br and I ΔH0 becomes more negative in the group (cuz of the energy as mentioned)
Hydrogen reduces oxides, superoxides and peroxides (with metal - compounds). Write down the reactions.
reduces oxides (incomplete) at high temperature 2 MeO2 + H2 → Me2O3 + H2O MeO + H2 → Me + H2O • reduces superoxides MeO2 + 2 H2 → Me + 2 H2O • reduces peroxides Me2O3 + 3 H2 → 2 Me + 3 H2O
Alkali metals carbonates/hydrogen carbonate (bicarbonates) are formed by reaction of...?
the hydroxide and CO2 Industrial production of Na2CO3 & NaHCO3
Describe the molecular hydrogen (H2) as ligand to metals:
• electrons from H2 fill an empty σ-orbital in the metal • electrons from a full orbital in the metal atom goes into an antibonding σ*-orbital in H2
With which group(s) are salt hydrides formed? which bonds does it have compared to small metals as Li, Be and Mg
• formed by alkali and the large alkaline earth elements - reaction between metal and hydrogen • ion-like bonds • group 1 hydrides have NaCl structure • small metals in groups 1 (Li) and 2 (Be, Mg) have covalent character
Name biological relevance for crown ethers
• important for ion transport across membranes • high selectivity • a new field of research in soil science