peridoicity

• Reactions of period 3 elements with oxygen: Na

  4Na(s) + O2(g) ---> 2Na2O(s)

  -needs to be heated

  -vigorous reactions

  -bright yellow flame

  -produces white solid
• Reactions of period 3 elements with oxygen: Mg

  2Mg(s) + O2(g) ---> 2MgO(s)

  -needs to be heated

  -vigorous reaction

  -bright white flame

  -white solid produced
• Reactions of period 3 elements with oxygen: Al

  4Al(s) + 3O2(g) ---> 2Al2O3(s)

  -powdered Al needed

  -fast reaction

  -bright white flame

  -white powder produced
• Reactions of period 3 elements with oxygen: Si

  Si(s) + O2(g) ---> SiO2(s)

  -powdered Si needed

  -needs to be strongly heated

  -slow reaction

  -bright white sparkles

  -white powder produced
• Reactions of period 3 elements with oxygen: P

  4P(s) + 5O2(g) ----> P4O10(s)

  -needs to be heated

  -vigorous reaction

  -yellow or white flame

  -white clouds produced
• Reactions of period 3 elements with oxygen: S

  S(s) + O2(g) ---> SO2(g)

  -powdered S

  -needs to be heated

  -gentle reaction

  -blue flame

  -toxic fumes produced
• reaction of sodium with water

  -reacts vigorously with cold water

  2Na(s) + 2H2O(l) ---> 2NaOH(aq) + H2

  -sodium melts into a ball and moves across water until it disappears

  -hydrogen gas given off - effervescence

  -solution formed is strongly alkaline due to NaOH
• reaction of magnesium and water

  -reacts extremely slowly with cold water

  Mg(s) + 2H2O(l) ---> Mg(OH)2(aq) + H2(g)

  -solution formed is weakly alkaline as Mg(OH)2 is slightly soluble

  -when Mg heated in steam - reacts vigorously

  Mg(s) +H2O(g) ---> MgO(s) + H2(g)
• trends of period 3 elements: atomic radius

  -decreases across a period

  -nuclear charge and e- number increase

  -elements have same number of shells so shielding remains the same

  -nucleus attracts electrons more strongly pulling them closer

  -atomic radius and size of atoms decrease
• trends of period 3 elements: ionic radius

  -the distance between nucleus and outermost e- of ion

  -across period from Na+ to Si4+, ions get smaller due to increasing nuclear charge attracting outer e- in second principal quantum shell

  -cations are smaller than original

  -anions are larger than original - gained e- in 3rd pqshell

  -increases repulsion between e- while nuclear charge is the same, causing e- cloud to spread out

  -P3- to Cl- ionic radii decreases as fewer e- are gained
• trends of period 3 elements: first ionisation energy

  -general increase

  -nuclear charge increases

  -atomic radii decreases

  -stronger attractive forces between nuclei and outer e-

  -gets harder to remove e-
• trends of period 3 elements: melting point

  -rises until Si then falls

  -Na to Al is metallic bonding

  -Si is covalent with giant molecular structure

  -P to Cl is covalent with simple molecular

  -Ar is simple molecular
• trends of period 3 elements: melting point explained

  -Na will donate e- into sea of delocalised

  -Mg will donate 2e- into sea

  -Al donates 3e- to sea, bonding is stronger in Al than Na

  -Si has highest point because giant molecular held together by 4 strong covalent bonds

  -P, S, Cl and Ar are non-metallic and exist as simple molecules

  -contains weak instantaneous dipole-induced dipole forces
• trends of period 3 elements: electrical conductivity

  -Na to Al increase number of valence e-

  -more available e- in Al so better conductor

  -Si not at all - giant molecular structure w/ 4 covalent bonds so no free moving e-

  -lack of delocalised from P to S