Learning objectives - - тотығу және тотықсыздану үрдісі су ерітіндісінде орын алатындығын түсіну; - -тотығуға және тотықсыздануға қатысты иондық-электрондық жартылай реакциялар теңдеулерін анықтау және жазу; - -тотығу дәрежесінің мәнін түсіну және оны элементтердің атауларында қолдану;
• Oxidation numbers are determined by the number of electrons gained or lost by an atom to reach “stability” • Electrons given up –Positive oxidation number • Electrons taken on –Negative oxidation number
• They are used to identify substances that have been reduced or oxidized in a reaction • Oxidation involves an increase in oxidation state • Reduction involves a decrease in oxidation state • Used in naming compounds
Rules for assigning oxidation number
Rule 1 The oxidation number of Oxygen is usually -2 except for peroxides e. g the oxidation number of oxygen in H 2 O=-2 Question What is the oxidation number of oxygen in (a) Na 2 O
Rule 2 The oxidation number of Flourine is usually -1 since it is e most electronegative e. g the oxidation number of flourine in HF=-1
Rule 3 • The oxidation number of Hydrogen= +1 except when combined with metals • e. g calculate the oxidation number of hydrogen in H 2 O and in Na. H
Rule 4 • The oxidation numbers of elements in group 1 and 2 equals to the group number and for aluminium=+3 • E. g the oxidation number of Na =+1 and Mg=+2
Rule 5 Any element, when not combined with atoms of a different element, has an oxidation number of zero. e. g the oxidation number of oxygen in O 2 =0
Rule 6 The sum of oxidation numbers is zero for a neutral compound. e. g the sum of oxidation number in Mg. O=0 Question What the sum of oxidation number in Li. Mn. O 4
Question • Calculate the oxidation number of chromium in Cr 2 O 3
Rule 7 Any simple monatomic ion (oneatom ion) has an oxidation number equal to its charge. e. g the oxidation number of sodium in Na+ =+1 question What is the oxidation number of oxygen in O-2?
Rule 8 The sum of the oxidation numbers of all of the atoms in a formula must equal the charge written for the formula. e. g the sum of oxidation number in carbonate, CO 3 -2 =-2 Question What the sum of oxidation number in PO 4 -3
Question Calculate the oxidation number of manganese, Mn in Mn. O 4 -
Oxidation numbers and formulas • Some metals have more than one oxidation number. • These are usually written with a roman numeral after them. • The roman numeral is the oxidation number.
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OXIDATION NUMBER.pptx