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Activity Series
Activity
Series of Metals: Predicting Reactivity
by Todd Helmenstine
The activity series of metals is
an empirical tool used to predict products in displacement reactions and
reactivity of metals with water and acids in replacement reactions and
ore extraction.
It can be used to predict the
products in similar reactions involving a different metal.
Exploring
the Activity Series Chart
The activity series is a chart of metals listed in order of
declining relative reactivity.
The top metals are more reactive than the metals on the bottom.
For
example, both magnesium and zinc can react with hydrogen ions to displace H2 from
a solution by the reactions:
Mg(s)
+ 2 H+(aq) →
H2(g) +
Mg2+(aq)
Zn(s)
+ 2 H+(aq) →
H2(g) +
Zn2+(aq)
Both
metals react with the hydrogen ions, but magnesium metal can also displace zinc
ions in solution by the reaction:
Mg(s)
+ Zn2+ →
Zn(s) + Mg2+
This
shows magnesium is more reactive than zinc and both metals are more reactive
than hydrogen.
This third displacement
reaction can be used for any metal that appears lower than itself on the
table.
The further apart the two
metals appear, the more vigorous the reaction.
Adding a metal like copper to
zinc ions will not displace the zinc since copper appears lower than zinc on
the table.
The
first five elements are highly reactive metals that will react with cold water,
hot water, and steam to form hydrogen gas and hydroxides.
The
next four metals (magnesium through chromium) are active metals that will react
with hot water or steam to form their oxides and hydrogen gas.
All the oxides of these two
groups of metals will resist reduction by H2 gas.
The
six metals from iron to lead will replace hydrogen from hydrochloric, sulfuric
and nitric acids.
Their oxides can be reduced by heating with hydrogen gas,
carbon, and carbon monoxide.
All
the metals from lithium to copper will combine readily with oxygen to form their
oxides.
The last five metals are
found free in nature with little oxides. Their oxides form through alternate
pathways and will readily decompose with heat.
The
series chart below works remarkably well for reactions that occur at or near
room temperatures and in aqueous solutions.
Activity
Series of Metals
Metal
|
Symbol
|
Reactivity
|
Lithium
|
Li
|
displaces H2 gas from
water, steam and acids and forms hydroxides
|
Potassium
|
K
|
|
Strontium
|
Sr
|
|
Calcium
|
Ca
|
|
Sodium
|
Na
|
|
Magnesium
|
Mg
|
displaces H2 gas from
steam and acids and forms hydroxides
|
Aluminum
|
Al
|
|
Zinc
|
Zn
|
|
Chromium
|
Cr
|
|
Iron
|
Fe
|
displaces H2 gas from
acids only and forms hydroxides
|
Cadmium
|
Cd
|
|
Cobalt
|
Co
|
|
Nickel
|
Ni
|
|
Tin
|
Sn
|
|
Lead
|
Pb
|
|
Hydrogen
gas
|
H2
|
included for comparison
|
Antimony
|
Sb
|
combines with O2 to form
oxides and cannot displace H2
|
Arsenic
|
As
|
|
Bismuth
|
Bi
|
|
Copper
|
Cu
|
|
Mercury
|
Hg
|
found free in nature, oxides decompose with heating
|
Silver
|
Ag
|
|
Palladium
|
Pd
|
|
Platinum
|
Pt
|
|
Gold
|
Au
|
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