Period 3 elements and oxides - part 2

Draw the trend in first ionisation across period 3

Explain the decrease in first ionisation energy from Mg to Al

Jump to 3p sub shell which is further from nucleus

Explain the decrease in first ionisation energy from P to S

3p3 to 3p4, electron must pair up in orbital so light repulsion makes easier to remove

Draw the trend in melting and boiling points across period 3

Explain the increase in melting point from Na to Al

Cations increase in charge, cations decrease in size, more delocalised electrons means stronger electrostatic forces

Explain the high melting point of Si

Strong covalent bonds between atoms requires a lot of energy to overcome

Explain the trend in melting point from P to Ar

Slight increase from P to S as molecules contain more electrons so stronger Van der Waals forces, decrease from S to Ar as number of electrons decreases

Which period 3 elements conduct electricity, and what is the trend in those that do?

Na, Mg and Al only, Al3+ has more delocalised electrons so is best

Metal and water —> ?

Metal hydroxide + hydrogen

Metal + steam —> ?

Metal oxide + hydrogen

Flame test for Na

Yellow

Flame test for Mg, Al, Si

Bright white

Flame test for P4

Very white

Flame test for S8

Blue

Reaction of Na2O with water + equation

Dissolves, Na2O + H2O —> 2NaOH

pH of solution formed when Na2O dissolves in water

13

Nature of sodium oxide

Basic

Reaction of MgO with water + equation

Slightly soluble, MgO + H2O —> Mg(OH)2

pH of solution formed when MgO reacts with water

9

Nature of magnesium oxide

Weakly basic

Reaction of Al2O3 with water + equation ❇

Insoluble

Reaction of SiO2 with water + equation ❇

Insoluble

Describe the difference observed when SO2 vs SO3 reacts with water

SO2 dissolves while SO3 dissolves and reacts violently

pH of solution when P4O10 or SO2 reacts with water

3

pH of solution formed when SO3 reacts with water

0/1

Reaction of Na2O with acid

Na2O + 2H+ —> 2Na+ + H2O

Reaction of MgO with acid

MgO + 2H+ —> Mg2+ + H2O

Reaction of Al2O3 with acid

Al2O3 + 6H+ —> 2Al3+ + 3H2O

Reaction of Al2O3 with alkali

Al2O3 + 2OH- + 3H2O —> 2Al(OH)4 -

Nature of aluminium oxide

Amphoteric

Reaction of SiO2 with alkali

SiO2 + OH- —> SiO3 2- + H2O

Conditions needed for SiO2 to react with alkali

Hot and conc NaOH

Reaction of P4O10 with alkali

P4O10 + 12OH- —> 4PO4 3- + 6H2O

Reaction of SO2 with alkali

SO2 + 2OH- —> SO3 2- + H2O

Reaction of SO3 with alkali

SO3 + 2OH- —> SO4 2- + H2O