The notion of oxidation number is introduced for the convenience of chemists and is necessary in treating reactions of oxidation and reduction. The oxidation number is equal to the ionic charge for substances containing ionic bond. For example in sodium chloride, NaCl, the oxidation number for Na is +1 and for Cl is –1. The oxidation number in the covalent bond substances is formed when all bonds in the molecules are considered as ionic. For example in the molecule of HCl, the hydrogen atom has oxidation number +1 and the oxidation number of chlorine atom is –1. The sum of the oxidation numbers of all the atoms in a particle must be equal to the charge of the particle.

Valence is specific property of the atoms. Valence can be defined as the number of electrons with which the atoms participate in forming of chemical bonds.

• Oxidation number
• Valence
• Electronegativity
• Problems and tests

Oxidation number

http://stezlab1.unl.edu/Chem251/Review/Covalent_Bonding/oxidation_numbers.htm Determining oxidation numbers, example - HNO_3.

http://www.chemistry.ucsc.edu/teaching/Winter98/Chem1C/Ox_num.html Rules for determining oxidation numbers.

http://www.chemistrycoach.com/oxno.htm Two methods and many examples for determining oxidation numbers.

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Valence

http://www.colorado.edu/physics/2000/periodic_table/valence_pattern.html Determining the valence.

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Electronegativity

http://dl.clackamas.cc.or.us/ch104-08/electron.htm Definition of “electronegativity of elements”.

http://www.scidiv.bcc.ctc.edu/wv/5%27/0005-008electronegativity.htm Describe how electronegativity changes across a row in the periodic table and from the top to bottom of a group.

http://www.chem.neu.edu/courses/reiff/b/lect09/ppframe.htm - Calculating electronegativity.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Electronegativity.html The relative electronegativity of two interacting atoms plays a major part in determining what kind of chemical bond forms between them.

http://www.chemguide.co.uk/atoms/bonding/electroneg.html#top How and why the electronegativity varies around the Periodic Table?.

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Problems and tests

ttp://www.usm.maine.edu/~newton/Chy2512_53/Lectures/   Formal charge, assigning electrons, oxidation numbers, valency and electronegativity.

http://www.usm.maine.edu/~newton/Chy251_253/   Formal charge, assigning electrons, oxidation numbers, valency and electronegativity.

http://www.chemistrycoach.com/   Formal charge, assigning electrons, oxidation numbers, valency and electronegativity.

http://www.chemistrycoach.com/ Formal charge, assigning electrons, oxidation numbers, valency and electronegativity.

http://www.learn.co.za/content/grade11/Science/chem_bonding/chem_bond/Unit4/ Formal charge, assigning electrons, oxidation numbers, valency and electronegativity.

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