Period 3 Flashcards
Which element is more reactive
sodium or magnesium?
- Sodium
- Less energy to lose 1 e- than 2
- More energy is needed for Mg to react
What happens when sodium reacts w/ water?
- React vigorously, forming molten ball on surface, fizzing + producing H2 gas
- Forms sodium hydroxide, alkaline (pH 12-14)
What happens when magnesium reacts w/ water?
- Cold water:
- Forms weak alkaline solution (pH 9-10) + thin coating of magnesium hydroxide forms on surface of metal
- Weak bc Mg(OH)2 isn’t v soluble, few H+ produced
- Steam:
- Reacts faster
- Forms magnesium oxide
Outline why the metal oxides have a high melting point
- Form giant ionic lattice
- Strong electrostatic FOA btw oppositely charged ions
- Requires alot of energy to overcome
Why does MgO have a higher MP than Na2O?
MgO forms 2+ ions so bonds more strongly than 1+ Na ions
Why does Al2O3 have a lower MP than expected?
Highly charged Al3+ distort oxygen’s e- cloud making bonds partially covelant
Why does SiO2 have a higher MP than the other non-metals?
- Giant macromolecular
- Strong covelant bonds need to be broken
- Require alot of energy to overcome
Why do P4O10 + SO2 have low MP?
- Form simple molecular
- Bound by weak IMF
- Low energy needed to overcome
What happens when the oxides of Na + Mg (ionic oxides) react w/ water?
- O2- accept protons from water molecules → OH-
- Forms alkaline sol
- Sodium hydroxide is more soluble so more alkaline
What happens when the oxides of P + S (simple covelant oxides) react w/ water?
- Form acidic sol
- They will dissociate forming H+ + -ve ions
What happens when water is reacted w/ silicon dioxide (giant covelant structure)?
- Insoluble in water
- Reacts w/ bases to form salts so classed as acidic
What happens when water is reacted w/ aluminium oxide?
- Partially ionic + covelant
- Insoluble in water
- Reacts w/ acids + bases - amphoteric
