1: Intro to main group chem Flashcards
topic 1
Metals
Characterised by ability to lose outer valence electrons.
High thermal and electrical conductivity
In solid state = cations
Shiny, malleable, ductile
Tend to form cations (+) and ionic compounds
Semi-metals/metalloids
Properties between metals and non-metals
Typically semiconductors (conduct heat and electricity moderately well)
Non-metals
Characterised by tendency to hold onto their valence electrons
Generally non-conductive
Tend to form anions (-) and molecular compounds (covalent)
How to get hydrogen?
- industrially:
C + H2O –> CO +H2
CH4 + H2O –(Ni)–> CO + 3H2
CO + H20 –(FeO)–> CO2 + H2 - Lab:
Mg + 2H+ –> Mg+2 + H2 - Electrolysis:
electricity splits water
Hydrogen + reactive metals
Ionic hydride (salt)
Hydrogen + nonmetals
Covalent hydrides
Hydrogen + metal crystal structure
Metallic Hydride
H fills gaps
Group 1
- Alkali metals
- react with water to form alkaline (very basic) solution
- soft, shiny grey metals
- low b.p
- very reactive
- stored under oil
- react violently with water and acids
Lithium carbonate (Li2CO3)
Drug for bipolar disorder
Used in manufacture of ceramics and toughened glass
Precursor for Li ion battery manufacture
Potassium Nitrate (KNO3)
Powerful oxidising agent
Gunpowder
Fireworks
Sodium Hydroxide (NaOH)
Important industrial base
Used to make bleach
2NaOH + Cl2 –> NaClO + NaCl + H2O
Used as drain cleaner
Manufacture of paper/textiles
Group 2
Alkaline Earth metals
Harder & denser than alkali metals but less than transition metals
Similar b.p to alkali metals
Reactivity increases down group
Applications of Mg and Ca
Abundant
Mg: silver metal, malleable, ductile at high temp
- forms strong low density alloys with Al and Zn
Ca: mineral
- essential for bones and teeth
lead to water hardness
Beryllium
High charge density = polarises nearby electron clouds
Extensive orbital overlap = lots of covalent character
Electron deficient in linear structure
BeCl
Becomes octet at lower temps when solid as chains form and join together
Boron
Electron deficient
BF3
Always covalent
React with nucleophile NH3 satisfies octet rule
Can form large cages
Aluminium
Can react with acids and bases
AlX3 exist as covalent dimers Al2X6 in the gas phase
Ligand
ions or neutral molecules that bond to a central metal atom or ion
Allotropes
different forms of the same element in the same physical state
very different physical properties
Carbon allotropes
Diamond
Graphite
Buckminsterfullerene
Amorphous carbon
Graphene
Diamond
Tetrahedral/sp3
Very hard
Colourless
Insulator
Graphite
Trigonal planar/sp2
Soft and greasy
Shiny black
Conducts electricity
Layers can slide over each other - lubricant
Lead in pencils
Buckminsterfullerene
Planar - spherical
C60
Mix of hexagons and pentagons
Amorphous carbon
Coal/charcoal
No crystalline structure
Graphene
Single layers of graphite
Flat or rolled into cylinders
Nanotech
Nitrogen
Haber process = ammonia
NH3 used in fertilisers, explosives, polymers, acrylics
Hydrogen bonding
N2O mild anaesthetic
Phosphorous
Extremely flammable
White phosphorous:
- P4
- tetrahedra
- waxy solid
- stored under water
- bursts into flame in air
- strong bond strain
Red phosphorous:
- P4
- polymeric chains
- red powder
- more stable
- non toxic
Oxygen allotropes
O2: oxygen
O3: Ozone
- protective UV absorbing layer
Oxygen
Combines mostly to give oxides
Noble gases
Extremely low b.p and m.p
Gases
Very stable
