U2 S3- Period 3 Elements Flashcards
sodium reaction with cold water
2Na + 2H2O —> 2NaOH + H2
Sodium reaction with cold water observation
1-Vigorously 2-molten ball on surface 3-effervescence 4-H2 gas 5-NaOH (strong alkaline solution)
Magnesium reaction with cold water
Mg + 2H2O –> MgO + H2
Magnesium reaction with cold water observation
1- reacts very slowly
2-Mg(OH)2 (weak alkaline))
why is the solution of Mg(OH)2 weakly alkaline
- Mg(OH)2 is not very soluble in water
- so few OH- ions produced
Magnesium reacts faster with
1-steam
2-more kinetic energy to form MgO
Magnesium reaction with steam
Mg + H2O –> MgO + H2
Period 3 reactions with air and rate
2Na + 1/2O2 --> Na2O VIGOUROUS Mg + 1/2O2 --> MgO VIGOROUS 2Al + 1 1/2O2 --> Al2O3 SLOW Si + O2 --> SiO2 SLOW P4 + SO2 --> P4O10 SPONTANEOUSLY COMBUSTS S + O2 --> SO2 BURNS STEADILY
Na and O2 colour flame
2Na + 1/2O2 –> Na2O YELLOW + WHITE PTT
Mg and O2 colour flame
Mg + 1/2O2 –> MgO BRILLIANT WHITE + WHITE PTT
Al and O2 colour flame
2Al + 1 1/2O2 –> Al2O3 N/A + WHITE PTT
Si and O2 colour flame
Si + O2 –> SiO2 N/A + WHITE PTT
P and o2 colour flame
P4 + SO2 –> P4O10 BRILLIANT WHITE + WHITE PTT
s and O2 colour flame
S + O2 –> SO2 BLUE + COLOURLESS GAS (SO2)
Catalyst with SO2 + 1/2O2 –> SO3
-vanadium (V2O5)
amphoteric
has properties of acid and base
Melting points of Na2O, MgO, Al2O3
1- Giant ionic lattices
2-strong forces of electrostatic attraction between positive ions and e-
Why is the melting point of MgO higher than Na2O
1- Mg2+ attract O2- more strong electrostatic attraction
than the 2 na+ attracted to O2-
2-more energy required to break ionic bonds
why is Al2O3 melting point lower than expected
1- Al3+ ions distort the oxygen’s electron cloud making it partially ionic and partially covalent
SiO2 melting point
1-Macromolecular/Giant covalent
2-Strong covalent bonds
3-lots of E required to break
4-High MP
melting points of P4O10 and SO3
1-simple molecular/compounds
2-molecules attracted by weak IMF VDWS and induced dipole-dipole
3-Low MP
Reactions of Na2O and MgO with water
Na2O + H2O –> 2NaOH
MgO + H2O –> Mg(OH)2
why is NaOH strongly alkaline and Mg(OH)2 weakly alkaline
NaOH= more soluble in water Na+ and OH- easier to dissociate into almost completely Mg(OH)= less soluble in water Mg2+ and OH- harder to dissociate into slightly
SiO2 reactions with water
1-SiO2 macromolecular / giant covalent
2-insoluble in water
