Week 5 -G1- Content Flashcards
Hydrogen and Alkali Metals: Pros and cons
- Pros:
- Forms a monopositive
ion H+ - Has a single s electron
- Cons:
- Is not a metal (but it can
be under extreme
conditions) - Does not react with
water
Hydrogen and Halogens: Pros and cons
- Pros:
- Is a non-metal
- Forms a diatomic
molecule - Cons:
- Rarely forms H-
(but does
occasionally) - Is comparatively
nonreactive
Ionic (Saline) Hydrides:
-Important class of hydrogen containing materials have
hydrogen in a (–1) oxidation state.
-Group 1 or 2 cations (CaH2
, NaH)
-Properties include:
1) Very reactive with water and oxygen
* NaH + H2O → NaOH + H2
* CaH2 + O2 →CaO + H2O
2) Excellent reducing agents:
* SiCl4 + 4 NaH → SiH4 + 4 NaCl
Covalent (Molecular) Hydrides:
- Hydrogen has access to its three possible
oxidation states:
–> +1: this is typical acid-base chemistry
and leads to hydrogen bonding
H2O, NH3, HF
–> 0: the majority of covalent hydrides
are covalent compounds
hydrocarbons, phosphine (PH3),
tin hydride (SnH4)
–> -1: the typical example is boron hydride
(diborane)
Group 1 Alkali Metals: Properties and Trends
- Shiny, silver metals when in the 0 oxidation
state. - Soft, low-melting, easily atomized, low density
(Weakly bonded metals). - High electrical and thermal conductivity.
Group 1 Alkali Metals: Chemistry
- Excellent reducing agents.
- React vigorously with water to form hydrogen:
2 Na + 2 H2O → 2 NaOH + H2 - Highly exothermic and the hydrogen formed may ignite in air.
- Vigor increases going down the group.
- React with oxygen to form oxides, peroxides, superoxides
Lithium Reagents:
- Very important in synthesis.
- Lithium forms covalent bonds with a range of
nuclei that other alkali cations don’t (e.g. carbon). Because it can polarize electron density
from the other nuclei. - Due to its ability to form covalent bonds, lithium is
combined with chloroalkanes to produce
alkyllithium compounds. This allows for nucleophilic carbon containing
species to be prepared.
Lithium honarary G2:
- Because its charge density is high, unlike the rest of
the alkali metals, and like the alkali earth metals,
lithium has much more in common with the alkali
earth metals in terms of chemistry. - Li is very similar to Mg, called a “diagonal
relationship”. - Due to diagonal relationship, Li+ substitutes for Mg2+ in
an enzyme process (inositol-monophosphatase).
Li unique properties:
- It is the only group member to spontaneously react with
dinitrogen.
has an extremely negative reduction potential,
making it desirable as a battery material.
- Lithium ion:
– Rechargeable, high energy density batteries
– Li+ ions migrate as the cell is charging
– Hybrid cars, consumer electronics
Cobalt…
- Early 20th century: use of cobalt in various alloys and as a catalyst in the
chemical industry. - 1990: Co was used for very hard superalloys with distinct magnetic
properties and high temperature resistance. - Now: rechargeable battery industry – 58% of use!!! LiCoO2
is the
cathode material in lithium-ion batteries.
Cobalt Production:
- present in low concentration in ores and is considered to be a
companion metal
-by-product of extraction
of commodities such as copper (~55%), nickel (~35%), and arsenic.
-Democratic Republic of Congo (DRC) account for
~70% of global production
Ethical Concerns with Cobalt Production:
- Poverty: 73% of the
DRC lives in extreme
poverty. - Health: Public health
crisis due to increased
rates of lung and skin
diseases. - Child labor: Human rights violations in DRC mines.
- ~40,000 children are employed in artisanal mining.
- Artisanal mines: small scale informal mines accounting for ~15% of
Congo’s cobalt.
Sustainability (3):
- Responsible Sourcing and Mining
- Alternative Extraction Techniques
- Circular Economy
What is a circular economy?
- A means of continuing production in a sustainable and environmentally
friendly way.
-A system based on the reuse and regeneration of materials and
products.
