REVIEWTOPIC 3/13: PERIODICITY
A. KEY DEFINITIONS (MEMORIZE!)
 First ionization energy - the energy needed to remove an electron from a gaseous atom or the energy needed to
remove one mole of electrons from one mole of gaseous atoms [i.e. X(g)  X(g)+ + e-]
 Electronegativity - a measure of the ability of an atom to attract a shared pair of electrons toward itself
 A ligand is a molecule or anion that donates a pair of electrons to a central metal ion, forming a dative covalent
bond
B. YOU SHOULD KNOW:
 Elements are arranged in order of increasing atomic number
 The table is arranged in groups, which are vertical, and periods, which are horizontal.
 Atomic radii increase down a group, because new electron shells are added, and decrease across a period, because
electrons are held more tightly by increasing effective nuclear charge
 The first ionization energy generally increases across a period and decreases down a group
 Electronegativity is highest for fluorine and decreases down the table and to the left of fluorine, as atomic radii
increase and attraction for the electrons is comparatively lower
 The ionic radii of cations (positive ions) are smaller than the corresponding atomic radii, because the remaining
electrons are held more tightly
 The opposite is true for anions; the ionic radii of anions (negative ions) are larger than the corresponding atomic
radii, because increased electron repulsion makes the radii larger.
 The following details about the oxides of period 3:
Groups
Acid/Base
Bonding
Examples
1 and 2
Basic
Ionic
Na2O, MgO
13
Amphoteric
Ionic
Al2O3
14
Acidic
Covalent
SiO2 (reacts with NaOH but not H20!)
15 to 17
Acidic
Covalent
SO2, SO3, NO2, P4O10
 The characteristic properties of transition metals are: variable oxidation states, formation of complex ions,
magnetic properties, existence of coloured compounds and ability to catalyze reactions
 Zn and Sc are not considered as transition metals as they do not have an incomplete d sub-level in their ions
 Examples of transition metal catalysts, such as Fe in the Haber Process and in heme, Ni in the conversion of
alkenes to alkanes, Pt and Pd in catalytic converters, and V2O5 in the Contact process
 Transition metals form complex ions when they are joined to ligands in solution
 How to describe/define coordinate covalent bonding in a complex and the coordinate number of the ion in the
complex
 Define electron affinity [X(g) + e-  X(g)- ]; identify/explain trend with respect to electron affinity
C. YOU SHOULD BE ABLE TO:
* Explain the ability of transition metals to form variable oxidation states from successive ionization energies
 Relate the electron arrangement of an element to the position in the periodic table (for example, if an element is
in period 3, it will have three shells of electrons)
 Relate the number of electrons in the valence shell (outer shell) to the group number (for example, magnesium is
in group 2, so it has two electrons in its outer shell).
 Compare the reaction of the alkali metals with water, for example: 2Na(s) + 2H 2O(l)  2NaOH(aq) + H2(g)
 Compare the reactions of the alkali metals with halogens, for example: 2Na(s) + Cl 2(g)  2NaCl(s)
 Show how halogens react with halide solutions, for example: 2NaBr(aq) + Cl2(aq)  2NaCl(aq) + Br2(aq)
 Write equations for the reactions of Na2O, MgO, P4O10 and SO2 with water.
 Explain that some complex ions are coloured because the d-orbitals split and electron transitions take place,
absorbing energy from the visible spectrum and causing the complementary colour to be seen (for example, if red
light is absorbed, the complex will appear blue).
 Draw a diagram showing the splitting of the d-orbital subshell
 Identify the factors that affect the extent of d-orbital splitting – (i.e., identity of the metal ion, oxidation state of
the metal ion, nature of the ligand, geometry of the complex ion)
 Explain the effect of different ligands on the splitting of d-orbitals in transition metal complexes using the
spectrochemical series provided in the data booklet
 Sketch the 3-D representation of an octahedral complex ion
 Determine the denticity of a ligand

Explain the magnetic properties in transition metals (whether a complex is paramagnetic or diamagnetic) in terms
of unpaired electrons.
D. BE PREPARED
 The data booklet contains information on all the periodic table trends. It is therefore very important that you can
explain the trends rather than just describe them.
 Non-metal oxides are responsible for acid rain, and you should know the source of these oxides. (e.g., industry, car
exhaust, natural sources – volcanoes, atmospheric CO2)