Man's physical universe

xanabras

UNIT VIII

SECTION 6

ATOMS DIFFER IN THEIR TENDENCY TO LOSE

ELECTRONS

Introduction.

It is now known that the elements differ in their tendency to release

and accept electrons.

A very important type of chemical reaction is

based on the transfer of electrons from one substance to another.

electrochemical industry, battery action and cell

of ores,

The

action, the smelting

the corrosion of metals, and many other important types of

chemical changes are examples of the transfer of electrons.

Three Tjrpes of Chemical Reactions Have Been Recognized.

There are three main types of polar reactions, proton transfer, double

decomposition, and electron transfer.

Reactions involving proton transfer

will be discussed in Sections 7 and 8 of this Unit. Double decomposition

reactions simply involve recombinations of ions in solutions

which result from ions being removed from solution by any one of the

methods which cause electrovalent reactions to go to completion.

Such reactions were discussed on p. 589.

There are four important types of electron transfer reactions: (1) decomposition,

(2) direct union, (3) displacement, and (4) oxidationreduction.

Decomposition, in general, refers to the breaking-down of one compound

to form two or more simpler compounds or elements; for

example, mercuric oxide, when heated, gives mercury and oxygen;

2HgO —>- 2Hg + O2

mercuric oxide mercury oxygen

Direct union is the opposite of decomposition; for example, iron

combines with oxygen in the presence of water to form iron oxide

(rust):

4pe ^ 2,0^ —>- 2 Fe^Oa

iron oxygen iron oxide

Displacement is the displacement of an element from its compound

by another element which takes its place, setting the original element

free.

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