1: Intro to main group chem

Question 1

Metals

Answer 1

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

Question 2

Semi-metals/metalloids

Answer 2

Properties between metals and non-metals
Typically semiconductors (conduct heat and electricity moderately well)

Question 3

Non-metals

Answer 3

Characterised by tendency to hold onto their valence electrons
Generally non-conductive
Tend to form anions (-) and molecular compounds (covalent)

Question 4

How to get hydrogen?

Answer 4

1. industrially:
   C + H2O –> CO +H2
   CH4 + H2O –(Ni)–> CO + 3H2
   CO + H20 –(FeO)–> CO2 + H2
2. Lab:
   Mg + 2H+ –> Mg+2 + H2
3. Electrolysis:
   electricity splits water

Question 5

Hydrogen + reactive metals

Answer 5

Ionic hydride (salt)

Question 6

Hydrogen + nonmetals

Answer 6

Covalent hydrides

Question 7

Hydrogen + metal crystal structure

Answer 7

Metallic Hydride
H fills gaps

Question 8

Group 1

Answer 8

• 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

Question 9

Lithium carbonate (Li2CO3)

Answer 9

Drug for bipolar disorder
Used in manufacture of ceramics and toughened glass
Precursor for Li ion battery manufacture

Question 10

Potassium Nitrate (KNO3)

Answer 10

Powerful oxidising agent
Gunpowder
Fireworks

Question 11

Sodium Hydroxide (NaOH)

Answer 11

Important industrial base
Used to make bleach
2NaOH + Cl2 –> NaClO + NaCl + H2O
Used as drain cleaner
Manufacture of paper/textiles

Question 12

Group 2

Answer 12

Alkaline Earth metals
Harder & denser than alkali metals but less than transition metals
Similar b.p to alkali metals
Reactivity increases down group

Question 13

Applications of Mg and Ca

Answer 13

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

Question 14

Beryllium

Answer 14

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

Question 15

Boron

Answer 15

Electron deficient
BF3
Always covalent
React with nucleophile NH3 satisfies octet rule
Can form large cages

Question 16

Aluminium

Answer 16

Can react with acids and bases
AlX3 exist as covalent dimers Al2X6 in the gas phase

Question 17

Ligand

Answer 17

ions or neutral molecules that bond to a central metal atom or ion

Question 18

Allotropes

Answer 18

different forms of the same element in the same physical state
very different physical properties

Question 19

Carbon allotropes

Answer 19

Diamond
Graphite
Buckminsterfullerene
Amorphous carbon
Graphene

Question 20

Diamond

Answer 20

Tetrahedral/sp3
Very hard
Colourless
Insulator

Question 21

Graphite

Answer 21

Trigonal planar/sp2
Soft and greasy
Shiny black
Conducts electricity
Layers can slide over each other - lubricant
Lead in pencils

Question 22

Buckminsterfullerene

Answer 22

Planar - spherical
C60
Mix of hexagons and pentagons

Question 23

Amorphous carbon

Answer 23

Coal/charcoal
No crystalline structure

Question 24

Graphene

Answer 24

Single layers of graphite
Flat or rolled into cylinders
Nanotech

Question 25

Nitrogen

Answer 25

Haber process = ammonia
NH3 used in fertilisers, explosives, polymers, acrylics
Hydrogen bonding
N2O mild anaesthetic

Question 26

Phosphorous

Answer 26

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

Question 27

Oxygen allotropes

Answer 27

O2: oxygen
O3: Ozone
- protective UV absorbing layer

Question 28

Oxygen

Answer 28

Combines mostly to give oxides

Question 29

Noble gases

Answer 29

Extremely low b.p and m.p
Gases
Very stable