Advanced A level inorganic chemistry - Periodic Table Periodicity Plots

11B(iii) Periodicity of the physical properties of elements Z = 1-96

Introduction

Periodicity means the regular occurrence of elements with similar properties giving repeating patterns when selected properties are plotted against proton/atomic number.

Graphs of the following physical properties for the elements Z = 1 to 96, 1st ionisation energy, atomic radius, electronegativity, melting point, boiling point, electrical conductivity and density are presented and explanations of the periodic trends discussed. The periodicity plots cover period 1, period 2, period 3, period 4, period 5, period 6 and the start of period 7.

Group numbering and the modern periodic table

The original group numbers of the periodic table ran from group 1 alkali metals to group 0 noble gases. To account for the d block elements and their 'vertical' similarities, in the modern periodic table, group 3 to group 0 are numbered 13 to 18. So, the 3d block elements Sc to Zn are now considered to be the top elements in groups 3 to 12. In more basic chemistry courses e.g. UK GCSE level, group numbers 1 to 0 are retained.

Sub-index for this page

(1) The periodicity of the 1st Ionisation enthalpy from elements Z = 1 to 96

(2) The periodicity of atomic radius from elements Z = 1 to 96

(3) The periodicity of electronegativity from elements Z = 1 to 96

(4) The periodicity of melting points and boiling points from elements Z = 1 to 96

(5) The periodicity of relative electrical conductivity from elements Z = 1 to 96

(6) The periodicity of density from elements Z = 1 to 96

(7) The periodicity of the molar volume from elements Z = 1 to 96

Two other plots available Z = 1 to 20 plots * Z = 1 to 38 plots * DATA

For non–advanced level students KS4 Science GCSE/IGCSE level Periodic Table notes links

(1) The periodicity of the 1st Ionisation enthalpy from elements Z = 1 to 96

The peaks correspond with the Noble Gases at the end of a period and the troughs with the Group 1 Alkali Metals at the start of a period.

There is a general increase in 1st ionisation energy from left to right across a period.

As you go across the period from one element to the next, the positive nuclear charge is increasing by one unit as the atomic/proton number increases by one unit and the charge is acting on electrons in the same principal quantum level.

The effective nuclear charge is approximately the number of outer electrons and this is increasing from left to right as no new quantum shell is added i.e. no extra shielding.

Therefore the outer electron is increasingly more strongly held by the nucleus and so, increasingly, more energy is needed remove it.

For the d blocks and f blocks, the increase is often more gradual as the sub–shells are filled with electrons of similar energy, though there are a few sub–troughs.

For more details for Periods 2 to 4 see Survey of Period 2 elements Z = 3 to 10,

Survey of Period 3 elements Z = 11 to 18 

and Survey of Period 4 elements Z = 19 to 36.

(2) The periodicity of atomic radius from elements Z = 1 to 96

The peaks correspond with the Group 1 Alkali Metals at the start of a period and the troughs with the Group 7 Halogens/Group 0 Noble Gases (data uncertain for Group 0) at the end of a period.

There is a general decrease in atomic radius from left to right across a period.

The atomic radius generally decreases from left to right across a period, as the actual and effective nuclear charge increases within the same principal quantum level with increase in proton number.

This effect pulls the electron cloud closer to the nucleus without any increase in shielding. The argument is almost identical to that for increasing ionisation energy.

For the d blocks and f blocks, the decrease is often more gradual as the sub–shells are filled with electrons of similar energy, though there are a few sub–peaks.

For more details for Periods 2 to 4 see Survey of Period 2 elements Z = 3 to 10,

Survey of Period 3 elements Z = 11 to 18 

and Survey of Period 4 elements Z = 19 to 36.

(3) The periodicity of electronegativity from elements Z = 1 to 96

The peaks correspond to the Group 7 Halogens/Group 0 Noble Gases at the end of a period and the troughs' correspond to the most electropositive Group 1 Alkali Metals at the start of a period.

There is a general increase in electronegativity from left to right across a period.

The electronegativity generally increases from left to right across a period, as the actual and effective nuclear charge increases within the same principal quantum level, pulling the electron cloud closer to the nucleus (see 1st IE arguments)

i.e. increase in proton charge without increase in shielding.

For the d blocks and f blocks, the increase is often more gradual as the sub–shells are filled with electrons of similar energy, though there are a few sub–troughs.

For more details for Periods 2 to 4 see Survey of Period 2 elements Z = 3 to 10,

Survey of Period 3 elements Z = 11 to 18 

and Survey of Period 4 elements Z = 19 to 36.

(4) The periodicity of melting points and boiling points from elements Z = 1 to 96

The melting points and boiling points tend to peak in the middle of  Periods 2 and 3 (Groups 3/13 and 4/14) and the lowest values at the end of the period – the Noble Gases. The highest values correspond to giant covalent or metallic lattice structures.

Generally you are moving from a low melting, but still quite high boiling, metallic lattice of the Alkali Metals of moderately strong bonding with one outer delocalised valence electron  ==> a much higher melting and boiling metallic or giant covalent lattice with 2–4 outer electrons for Groups 2 to 4/14 involved in bonding.

Most elements in the d and f blocks have relatively high melting points and boiling points with more d and f delocalised electrons contributing to the metallic bonding in the lattice.

After the d and f blocks, in Groups3/13 to Group 0/18, apart from a few semi–metals/metals you mainly have simple molecular species only held together by weak intermolecular forces.

For more details for Periods 2 to 4 see Survey of Period 2 elements Z = 3 to 10,

Survey of Period 3 elements Z = 11 to 18 

and Survey of Period 4 elements Z = 19 to 36.

(5) The periodicity of relative electrical conductivity from elements Z = 1 to 96

The peaks correspond to the metals in the middle of the period with the greatest number of outer electrons that can be delocalised.

Electrical conductivity increases dramatically from left to right for Groups 1–2 (and Al in Group 3/13 in Period 3) as the metallic lattice contains 1–2–3 mobile delocalised electrons involved in electrical conduction.

From Group 4 to 0 the element structure changes to giant covalent lattice, semi–metal or simple molecular structures with less tendency towards delocalisation or no free delocalised electrons at all, within the structure to convey an electric current.

All the elements in the d and f blocks have a fairly high electrical conductivity due to the extra delocalisation of the d and f electrons contributing to the electrical conduction in their metallic lattices.

For more details for Periods 2 to 4 see Survey of Period 2 elements Z = 3 to 10,

Survey of Period 3 elements Z = 11 to 18 

and Survey of Period 4 elements Z = 19 to 36.

(6) The periodicity of density from elements Z = 1 to 96

The peaks correspond to the metals in the middle of the period with the strongest bonding in the solid.

The density increases from lithium to beryllium as the atomic radii decrease and the bonding gets stronger with 1 ==> 2 bonding electrons (delocalised outer valency electrons in the metal lattice).

Boron and silicon have a lower density, typical of non–metallic covalent solids. Nitrogen, oxygen, fluorine and neon are small covalent molecules and have very low densities being gaseous at room temperature because only weak intermolecular forces act between them.

All the elements in the d and f blocks have a fairly high densities due to the extra delocalisation of the d and f electrons contributing to stronger bonding and lower atomic radii in their metallic lattices and the effect tends to peak ²/₃rds the way along a block.

For more details for Periods 2 to 4 see Survey of Period 2 elements Z = 3 to 10,

Survey of Period 3 elements Z = 11 to 18 

and Survey of Period 4 elements Z = 19 to 36.

(7) The periodicity of the molar volume from elements Z = 1 to 96

The peaks correspond with the least dense solid/liquid elements, the Group 1 Alkali Metals and is a historically important graph, first investigated by Lother Meyer in 1869 (see History of Periodic Table page).

The molar volume is the volume occupied by the relative atomic mass of the element in grams.

For my graph I've used the molar volume of the solid at room temperature and pressure (298K, 1 atm) or the volume of the liquified gas if the element is a gas at room temperature.

It is one of the clearest graphs you can plot to show the periodicity of an element's properties, but there are still 'inconsistencies' due to the complex behaviour of the orbital energy levels.

WHAT NEXT?

Z = 1 to 20 periodicity plots * Z = 1 to 38 periodicity plots * DATA