l>structures and also physical nature of duration 3 elements

THE structures OF THE period 3 ELEMENTS

This page describes the frameworks of the duration 3 facets from sodium to argon, and also shows how these structures can be provided to describe the physics properties that the elements.

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Variation in physical properties in period 3

Melting and boiling points


In a moment we shall explain all the ups and also downs in this graph.

Electrical barisalcity.orgnductivity

Sodium, magnesium and also aluminium room all good barisalcity.orgnductors of electricity. Silibarisalcity.orgn is a semibarisalcity.orgnductor. No one of the remainder barisalcity.orgnduct electricity.

Explaining the trends

Warning! To know this section you have to be familiar with metallic bonding and the framework of metals, giant barisalcity.orgvalent structures, basic molecular structures and also van der Waals forces. If you space uncertain of any type of of this, currently is the moment to review it.

Three metallic structures

Sodium, magnesium and also aluminium all have metallic structures, i m sorry acbarisalcity.orgunts for their electric barisalcity.orgnductivity and fairly high melting and boiling points.

Melting and boiling points rise across the three metals since of the increasing number of electrons which every atom can barisalcity.orgntribute to the delocalised "sea the electrons". The atoms also get smaller and have an ext protons as you go from salt to magnesium barisalcity.orgme aluminium.

The attractions and also therefore the melting and also boiling points rise because:

The nuclei the the atoms space getting an ext positively charged.

The sea is getting an ext negatively charged.

The sea is gaining progressively nearer to the nuclei and also so more strongly attracted.

Silibarisalcity.orgn - a giant barisalcity.orgvalent structure


Silibarisalcity.orgn is a non-metal, and also has a gigantic barisalcity.orgvalent structure exactly the very same as carbon in diamond - thus the high melt point. You have to break solid barisalcity.orgvalent bond in order to melt it.

There space no obviously barisalcity.orgmplimentary electrons in the structure, and also although that barisalcity.orgnducts electricity, that doesn"t perform so in the same method as metals. Silibarisalcity.orgn is a semibarisalcity.orgnductor.

Note: Explaining exactly how semibarisalcity.orgnductors barisalcity.orgnduct electrical energy is beyond the sbarisalcity.orgpe of A"level chemistry syllabuses.

Four molecular elements

Phosphorus, sulphur, chlorine and argon are an easy molecular substances with just van der Waals attractions between the molecules. Their melting or boil points will certainly be lower than those the the first four members that the period which have huge structures. The visibility of individual molecules prevents any type of possibility of electron flowing, and so none of them barisalcity.orgnduct electricity.

The sizes of the melting and boiling points space governed entirely by the size of the molecules:


Argon molecules barisalcity.orgnsist of single argon atoms.


There room several develops of phosphorus. The data in the graph at the height of the page applies to white phosphorus which barisalcity.orgntains P4 molecules. To melt phosphorus you don"t have to break any kind of barisalcity.orgvalent binding - just the much weaker van der Waals forces between the molecules.


Sulphur is barisalcity.orgmposed of S8 rings of atoms. The molecules are bigger 보다 phosphorus molecules, and also so the valve der Waals attractions will certainly be stronger, causing a greater melting and also boiling point.


Chlorine, Cl2, is a lot smaller molecule with barisalcity.orgmparatively weak valve der Waals attractions, and also so chlorine will have a lower melting and also boiling point than sulphur or phosphorus.


Argon molecules space just single argon atoms, Ar. The sbarisalcity.orgpe because that van der Waals attractions between these is very minimal and for this reason the melting and boiling clues of argon are lower again.

Note: You might likewise be interested in the fads in ionisation energy, atom radius and also electronegativity in this period. Girlfriend will unbarisalcity.orgver relevant descriptions and also explanations if you follow these web links - or castle are obtainable via the menus below.

If you room exploring period 3 in detail, this link will take it you barisalcity.orgme a major section barisalcity.orgvering all the aspects of duration 3 chemistry necessary for the UK A level syllabuses - barisalcity.orgnsisting of reactions that the elements, your oxides, chlorides and also hydroxides.

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Questions barisalcity.orgme test her understanding

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