Unit 1-1 Flashcards
What is valency?
A numerical measure of the combining power of an atom/ion
Historically the number of hydrogen atoms which will combine with one or a group of atoms
Note: The number of positive or negative charges in an ion
What is oxidation?
Loss of electrons
Addition of oxygen
Loss of hydrogen
Oxidation number increases
What is reduction?
Gain of electrons
Removal of oxygen
Gain of hydrogen
Oxidation number decreases
What are the rules of oxidation?
- The O.N of an element is 0
Cl2 has an O.N of 0 unless found in a compound - The sum of oxidation number in a neutral compound is 0
- In a compound containing hydrogen, hydrogen has an O.N of +1
Except in metal hydrides such as NaH and KH, hydrogen has an O.N of -1 and the metal becomes +1 - In a compound containing oxygen, oxygen has an O.N of -2
Except with fluoride or peroxides, where the O.N is multiplied by the number of oxygen atoms - In a compound containing a halogen, halogens have an O.N of -1
- Group 1 metals have oxidation numbers of +1 in compounds
- Group 2 metals have oxidation numbers of +2 in compounds
- In species with atoms of different elements, the most electronegative element is given the negative O.N
Electrons shown by the atoms charge aren’t included in the O.N
The oxidation number of oxygen in MnO4^- is -7
What does an oxidation number represent?
The number of electrons needed to be gained or lost for an element to become neutral
Example: Mg2+ needs to gain 2 electrons, the O.N is +2
What do oxidising agents do in a reaction?
Causes oxidation by gaining electrons in a reaction
Oxidation number decreases
What is an ionic equation?
A written chemical equation which only represents the particles which have changed state, charge, compound etc
What are spectator ions?
Particles which are unchanged in a reaction, and can therefore be removed in ionic equation
