THE ELEMENTS OF GROUPS IB AND MB 427
Silver has little tendency to formally lose more than one electron;
its chemistry is therefore almost entirely restricted to the + 1
oxidation state. Silver itself is resistant to chemical attack, though
aqueous cyanide ion slowly attacks it, as does sulphur or a sulphide
(to give black Ag 2 S), hence the tarnishing of silver by the atmosphere
or other sulphur-containing materials. It dissolves in concentrated
nitric acid to give a solution of silver(I) nitrate, AgNO 3.Oxidation state + 2
The only important compound is the paramagnetic silver(II)
fluoride, AgF 2 , prepared by fluorination of the metal; it is used as a
convenient fluorinatmg agent.Oxidation state +1
Addition of an alkali hydroxide to a solution of a silver(I) salt gives
a brown solid, silver(I) oxide, Ag 2 O; when wet this behaves as
"silver hydroxide' AgOH, for example
^AgOH' + C 2 H 5 I -» Agl + C 2 H 5 OH
iodethane ethanol
The oxide is soluble in ammonia to give the complex [Ag(NH 3 ) 2 ] +
(linear). On heating, silver(I) oxide loses oxygen to give the metal
(all the coinage metal oxides have low thermal stability and this
falls in the order Cu > Ag > Au).SILVER(I) HALIDES
While the chloride, bromide and iodide are insoluble in water, the
fluoride, AgF, is very soluble.
The insoluble halides can be prepared by adding the respective
halide ion to silver ions:
Ag+ +X-^AgXi
(halide)
The chloride is white, the bromide pale yellow and the iodide
deeper yellow. These are examples (uncommon) of a coloured com-
pound being obtained from colourless ions. The silver(I) ion
intensifies colour in other cases, for example silver chromate(VI),
Ag 2 CrO 4 , is brick-red while potassium chromate(VI). K 2 CrO 4. is
yellow.