The following notes were written for the previous IB syllabus (2009). The new IB syllabus for first examinations 2016 can be accessed by clicking the link below.

IB syllabus for first examinations 2016

Periodicity (sl)

3.1 - The Periodic Table

A list of the chemical elements arranged into Groups (the columns going down) and Periods (the rows going across). The group number gives the number of valence (outer shell) electrons around the atom. The period number is the same as that of the outer energy shell. Elements increase in atomic number across each period by one.

Example: Calcium is in the 2nd group therefore it has 2 electrons in the outer shell and a valency of +II. It is in the fourth period therefore its outer electrons are in the fourth energy shell.

Trends in physical properties

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3.2 - Physical Properties

Characteristic Trend (left to right) Reason
Atomic radius decreases in size from left to right increased attractive force (acting on the same energy shell) of the nucleus increases as the number of protons increases
Ionic radius decreases across the period until formation of the negative ions then there is a sudden increase followed by a steady decrease to the end In general as above. The sudden increase on formation of negative ions is due to the new (larger) outer shell
Electronegativity Increases More electron attracting power of the larger nuclear charge as we move to the right
Metallic character Decreases - Na, Mg, Al metals; Si metalloid; P, S, Cl, Ar non-metals Metallic character is a measure of the ease of loss of electrons from the outer shell. This decreases with increasing nuclear charge.
Melting point NaAl steady increase Increasing availability of electrons in the metallic bonding associated with greater charge density of the metal ion
Si massive increase Si giant macromolecular structure
P large decrease P4 molecules
S small increase S8 crown shaped molecules
Cl Ar decrease Cl2 molecules and Ar atoms

The elements of group 1

Characteristic Trend (descending group 1) Reason
Atomic radius increases in size top to bottom The number of electron shells increases from Li to Cs
Ionic radius increases from Li to Cs The number of electron shells increases from Li to Cs
Electronegativity decreases Attracting power of the nucleus is sheilded by the inner electron shells increasingly as the group is descended
Ionisation energy Decreases descending the group Sheilding effect of the inner electron shells increases as we descend the group and so the outer electron is more easily removed
Melting point Decreases from Li to Cs The larger ions have weaker metallic bonding as their charge density (charge/volume ratio)is smaller

The elements of group 7 (Fluorine to Iodine)

Characteristic Trend (descending group 7) Reason
Atomic radius increases in size from F to I The number of electron shells increases from F to I
Ionic radius increases from F to I The number of electron shells increases from F to I
Electronegativity decreases Attracting power of the nucleus is sheilded by the inner electron shells increasingly as the group is descended
Ionisation energy Decreases descending the group Sheilding effect (repusion caused by the inner electrons) of the inner electron shells increases as we descend the group and so the outer electron is more easily removed
Melting point Increases from F to I The larger halogens have greater Van der Waals forces holding the molecules together as they have more electrons
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3.3 Chemical Properties

Reactions of elements of the same group are similar because they have identical outer shells (ie same number of valence electrons). The following must be covered:

  • Reactions of group 1(alkali metals) and group 7 (halogens) elements with water
  • Reaction of group 1 (alkali metals) elements with group 7 (halogens)
  • Displacement reaction of halogens
  • Reaction of silver ions with halide ions (group 7 element ion)
  • Acidity/basicity of the element oxides
  • The metallic /non-metallic nature of the elements

Reactions of group 1 and 7

Element reagent example equation conditions (if any)
Group 1(Li...Cs) water 2Na + 2H2O --> 2NaOH + H2 violent reaction
Group 1(Li...Cs) halogen 2Na + Cl2 --> 2NaCl heat needed
       
Group 7 (halogen) water Cl2 + H2O HCl + HClO  
       

Displacement reaction of halogens

Reactivity of the halogens decreases going down the group and the more reactive halogen will displace a less reactive halogen from a solution of its ions. This is also a redox reaction.

  Cl-(aq) Br-(aq) I-(aq)
Cl2

Colorless / no reaction

turns red due to formation of bromine

turns brown due to formation of iodine

Br2

no reaction

no reaction

turns brown due to formation of iodine

I2

no reaction

no reaction

no reaction

The reactions of Halide ions with Silver ions

  Cl-(aq) Br-(aq) I-(aq)
Ag+

white ppt

cream ppt

yellow ppt

reason

insoluble AgCl formed

insoluble AgBr formed

insoluble AgI formed

equation

Ag+ + Cl- AgCl

Ag+ + Br- AgCl

Ag+ + I- AgI

Metallic character of the elements

Elements on the left are metallic...right are non-metals...Si is a metalloid.

Acidic character of the oxides

  • Metal oxides are basic

  • Aluminium oxide is amphoteric (reacts with both acids and bases)

  • Non-metal oxides are acidic

  Na2O MgO Al2O3 SiO2 P4O10 (or P4O6) SO3 (or SO2) Cl2O7
Adding H2O Na2O + H2O -> 2NaOH MgO + H2O -> Mg(OH)2 Insoluble Insoluble P4O10 + 6H2O -> 4H3PO4 SO3 + H2O -> H2SO4 Cl2O7 + H2O -> HClO4
Adding HCl Na2O + H+ -> 2Na+ + H2O MgO + 2H+ -> Mg2+ + H2O Al2O3 + 6H+ -> 2Al3+ + 3H2O No reaction No reaction No reaction No reaction
Adding NaOH No reaction No reaction Al2O3 + 2OH- + 3H2O -> 2Al(OH)4 SiO2 + 2OH- -> SiO32- + H2O P4O10 + 12OH- -> 4PO43- + 6H2O SO3 + OH- -> SO42- + H2O Cl2O7 + OH- -> 2ClO4- + H2O
Nature Basic Oxide Basic Oxide Amphoteric Oxide Acidic Oxide Acidic Oxide Acidic Oxide Acidic Oxide
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Resources

Ionic and atomic radii

Periodic trends ppt presentation

Atomic and ionic radii display (needs chime)


http://www.chem.ox.ac.uk/vrchemistry/periodic_table/Flash/Metallic%20or%20covalent%20basic.swf



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