Period 3 elements (Inorganic) (complete) Flashcards
Describe the trends in melting points in the period 3 elements.
Na, Mg, Al - high as the structures are metallic, so strong attraction between +ve metal atoms and cloud of delocalised outer shell e-, increase from Na to Al as metallic bonding strength increases due to more protons, smaller atoms and more delocalised e- per atom.
Si - giant covalent structure so highest melting points of all as need to break many strong covalent bonds.
P4, S8, CL2 - simple molecules so smaller than metallic but higher than Ar as only weak van der waals forces between molecules, but S8 strongest as bigger molecule so more e- so more va der waals forces.
Ar - monatomic so lowest m.p as very weak van der waals forces between atoms.
Describe the trend in atomic radius in the period 3 elements.
- General decrease across period.
> e- in same main shell.
> same amount of shielding.
> more protons in nucleus so higher attraction to e- so pulled closer to nucleus.
Describe the trend in electronegativity in period 3 elements.
- General increase across period.
> smaller atomic radius.
> more protons.
> so stronger nuclear attraction to the 2 e- in the covalent bond.
> (no Ar value as monatomic)
Describe the trend in ionisation energy in period 3 elements.
- General increase as smaller atomic radius but more protons so stronger nuclear attraction to outer e-.
Unexpected dip Mg to Al - Mg loses electron from 3s orbital, Al loses electron from 3p orbital, 3p orbital higher energy than 3s so easier to remove.
Unexpected dip P to S - P loses electron from orbital containing one e-, S loses electron from orbital containing 2 e- so more repulsion so easier to remove.
Describe the reaction of Na with water
- floats and moves rapidly across surface of water.
- exothermic.
- metal melts into sphere.
- fizzes.
Describe the two reactions of Mg with water.
(why are two required?)
(+water) - very slow, no visible reaction
(+steam) - bright white flame, white solid formed
- steam used as reaction it’s water too slow and no visible reaction seen.
Describe the reactions of Cl2 with water.
(+Cl2 disproportionation reaction) and (+Cl2 and sunlight)
- no visible reaction for both.
Describe the reaction of Na with oxygen.
- melts quickly when heated (sodium)
- white smoke formed (Na2O)
- yellow flame
Describe the reaction of Mg with oxygen.
- bright white light
- very exothermic
- white solid formed (MgO)
Describe the reaction of Al with oxygen.
Powder - highly exothermic, bright white flame, white solid formed
Foil - no visible reaction as Al coated with Al2O3
Describe the reaction of Si with oxygen.
- small amount of Mg powder used to begin reaction as can’t ignite Si with flame alone.
- very exothermic
- silicon burns very slowly
- white/grey solid formed Foil
Describe the reaction of P4 with oxygen.
- bright white light
- burns vigorously
- white solid formed Foil
Describe the reaction of S8 with oxygen.
- bright blue flame
- choking toxic gas (SO2)
Describe the reaction of Na2O with water
Na2+ and O2- ions dissolve in water, then O2- ions react with water.
Describe the reaction of MgO with water
- slightly soluble, some dissolves then react with water to form a solution
- some Mg2+ ions and O2- dissolves then O2- reacts with water.
Describe the reaction of Al2O3 with water
- insoluble due to very high lattice enthalpy
Describe the reaction of Si02 with water
insoluble due to lattice of atoms linked by strong covalent bonds that would have to be broken.
What is the condition for SiO2 reacting with a base?
- Must be conc, hot NaOH
Describe the reaction of P4O10 with water
- reacts violently
- water molecules attach to the delta +ve P atoms leading to H+ ion release from water molecules.
Describe the reaction of SO2 with water
- dissolves
- water molecules attach to the delta +ve S atoms leading to H+ release from water molecules.
Describe the reaction of SO3 with water
- reacts violently
- Water molecules attach to the delta +ve S atoms leading to H+ ion release in water molecules.
