1. Introduction to CHEMICAL BONDING

* GCSE Chemistry (& basic advanced) Chemical Bonding Notes Part 1 Introducing chemical bonding Doc B

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Doc Brown's Chemistry - Chemical Bonding - Revision Notes

Part 1 Introduction to the Chemical Bonding

Revision KS4 Science IGCSE/O level/GCSE Chemistry Information Study Notes for revising for AQA GCSE Science, Edexcel 360Science/IGCSE Chemistry & OCR 21stC Science, OCR Gateway Science (revise courses equal to US grades 9-10) Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA OCR Edexcel Salters CIE revising courses for pre-university students (equal to US grade 11 and grade 12 and Honours/honors level courses)

Part 1 Introduction - why do atoms bond together? (this page, read first)

and sub-index for Parts 2-5 (this page)

Part 2 Ionic Bonding - compounds and properties

Part 3 Covalent Bonding -small simple molecules and properties

Part 4 Covalent Bonding - macromolecules and giant covalent structures

Part 5 Metallic Bonding - structure and properties of metals

Part 6 More advanced concepts for advanced level chemistry (in preparation, BUT a lot on intermolecular forces in Equilibria Part 8)

* Keywords/phrases/names sub-index for Parts 2-5: Examples of ionic compounds described: sodium chloride NaCl (exemplar for any Li/Na/K + F/Cl/Br/I combination), magnesium chloride MgCl₂ (exemplar for any Mg/Ca + F/Cl/Br combination), aluminium fluoride AlF₃, potassium oxide K₂O (exemplar for any Li/Na/K + O/S combination), magnesium/calcium oxide MgO/CaO and magnesium/calcium sulphide (MgS/CaS), aluminium oxide Al₂O₃ (exemplar for Al₂S₃) * Examples of covalent molecules: simple small molecule bonding e.g. water * physical properties of small molecules * giant network bonding - giant molecules e.g. carbon C-diamond/graphite, silicon Si/silica SiO₂ * properties of giant covalent structures * polymers/plastics * properties of polymers * inter/intra (internal)-molecular forces * hydrogen H₂, chlorine Cl₂, hydrogen chloride HCl, water H₂O, ammonia NH₃, methane CH₄, oxygen O₂, carbon dioxide CO₂, ethene C₂H₄, nitrogen N₂, ethane C₂H₆, chloromethane CH₃Cl, methanol CH₃OH, carbon (diamond), carbon (graphite), carbon (buckminsterfullerene/fullerenes), silica/silicon dioxide SiO₂ * examples of ionic compounds * physical properties of ionic compounds *If your ionic compound is not listed, look for a compound with a similar formula and you should be able to work it out from the example given. The use of the word exemplar implies you are dealing with the same set of outer electron arrangements (configurations), which is why you can work out lots more dot and cross diagrams of ionic compounds by understanding one example * metal bonding model element/alloys * physical properties of metals *

Associated notes on other web pages:

Atomic Structure notes & diagrams including electron arrangements.

Models and properties of Gases, Liquids and Solids.

A brief survey-summary of the Periodic Table including electronic structure and formula patterns.

How to work out formula of ionic or covalent compounds without going through some demanding electronic thinking is described in the valency section on the "Elements, Compounds and Mixtures" page and it is followed by a section on naming compounds.

GCSE BONDING m/c QUIZZES: Foundation or Higher

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Part 1. Why do atoms bond together? - 'electron glue'!

Some atoms are very reluctant to combine with other atoms and exist in the air around us as single atoms. These are the Noble Gases and have very stable electron arrangements e.g. 2, 2,8 and 2,8,8 because their outer shells are full. The first three are shown in the diagrams below and explains why Noble Gases are so reluctant to form compounds with other elements.

(atomic number) electron arrangement

All other atoms therefore, bond together to become electronically more stable, that is to become like Noble Gases in electron arrangement. Bonding produces new substances and usually involves only the 'outer shell' or 'valency' electrons and atoms can bond in two ways.

The phrase CHEMICAL BOND refers to the strong electrical force of attraction between the atoms or ions in the structure. The combining power of an atom is sometimes referred to as its valency and its value is linked to the number of outer electrons of the original uncombined atom (see examples later).

(a) IONIC BONDING - By one atom transferring electrons to another atom to form oppositely charged particles called ions which attract each other - the ionic bond.

An ion is an atom or group of atoms carrying an overall positive or negative charge
- e.g. Na⁺, Cl^-, [Cu(H₂O)]²⁺, SO₄^2- etc.

If a particle, as in a neutral atom, has equal numbers of protons (+) and electrons (-) the particle charge is zero i.e. no overall electric charge.

The proton/atomic number in an atom does not change BUT the number of associated electrons can!

If negative electrons are lost the excess charge from the protons produces an overall positive ion.

If negative electrons are gained there is an excess of negative charge, so a negative ion is formed.
The charge on the ion is numerically related to the number of electrons transferred i.e. electrons lost or gained.

For any atom or group of atoms, for every electron gained you get a one unit increase in negative charge on the ion, for every electron lost you get a one unit increase in the positive charge on the ion.

The atom losing electrons forms a positive ion (cation) and is usually a metal. The atom gaining electrons forms a negative ion (anion) and is usually a non-metallic element. The ionic bond then consists of the attractive force between the positive and negative ions in the structure.
The ionic bonding forces act in all directions around a particular ion, it is not directional, as in the case of covalent bonding.

(b) COVALENT BONDING - sharing electrons to form molecules with covalent bonds, the bond is usually formed between two non-metallic elements in a molecule. The two positive nuclei (due to the positive protons in them) of both atoms are mutually attracted to the shared negative electrons between them - the covalent bond. They share the electrons in a way that gives a stable Noble Gas electron arrangement.

This kind of bond or electronic linkage does act in a particular direction i.e. along the 'line' between the two nuclei of the atoms bonded together, this is why molecules have a particular shape.

(c) METALLIC BONDING isn't quite like ionic or covalent bonding, the metal atoms form positive ions, but no negative ion is formed from the same metal atoms, but the positive metal ions/atoms are attracted together by the free moving negative electrons between them.

NOBLE GASES are very reluctant to share, gain or lose electrons to form a chemical bond. They are already electronically very stable. For most other elements the types of bonding and the resulting properties of the elements or compounds are described in detail in Parts 2 to 5. In all the electronic diagrams ONLY the outer electrons are shown.

New bonds formed! Poetry in motion!

Lots of energy released

Ionic Bonding Poem - a snippet of chemistry poetry

(anon Y11 student, Whitby Community College, Oct 31st 2002)

How do I long for a full outer shell!

being chlorine having seven, is a horrid hell

but my name is sodium and I have one spare!

I want to lose it, can we not share?

No? for are we not a perfect match

chuck it to me, I promise to catch

then we can live our separate ways

and live with full shells to the end of our days!

and so our tale comes to an end

as positive and negative we shall remain friends