A Level Notes on 1-96

7/27/2019 A Level Notes on 1-96

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(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. As you go across the period from one element to the next, the positive nuclear charge is increasing by one unit as the atomic/protonnumber 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 dblocks 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.

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(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 NobleGases (data uncertain for Group 0) at the end of a period. It generally decreases from left to right across a period, as the actual and effectivenuclear charge increases within the same principal quantum level with increase in proton number, pulls the electron cloud clo ser 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, thedecrease 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.











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(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 mostelectropositive Group 1 Alkali Metals at the start of a period. It generally decreases 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 theend 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 delocalisedvalence electron ==> a much higher melting/boiling metallic or giant covalent lattice with 2-4 outer electrons for Groups 2 to 4 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 tothe 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 elementsZ = 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. Increases dramatically from left to right for Groups 1-2 (and Al in Group 3 in Period 3) as the metallic lattice contains 1-2-3 mobiledelocalised 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 lithiumto 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 smallcovalent 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 peak2/3rds 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, firstinvestigated by Lother Meyer in 1869 (see History of Periodic Table page). The molar volume is the volume occupied by the relative atomic

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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 thevolume of the liquified gas if the element is gas at room temperature. It is one of the clearest graphs you can plot to show the periodicity of an

element's properties.

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A Level Notes on 1-96