Editing Reactivity series

{{Short description|Analytical progression of a series of metals arranged by their reactivity in descending order}}
{{distinguish|Electrochemical series}}

In chemistry, a '''reactivity series '''(or '''reactivity series of elements''') is an empirical, calculated, and structurally analytical progression<ref name="G&E" /> of a series of [[metal]]s, arranged by their "reactivity" from highest to lowest.<ref>{{citation | url = https://www.gcsescience.com/r1-reactivity-series-metals.htm | title = The Reactivity Series of Metals | first = Colin | last = France | year = 2008}}</ref><ref>{{citation | title = Science in Focus, Chemistry for GCE 'O' Level | first = J. G. R. | last = Briggs | page = 172 | publisher = Pearson Education | year = 2005}}</ref><ref>{{citation | title=Longman Pocket Study Guide 'O' Level Science-Chemistry | author = Lim Eng Wah | page = 190 | publisher = Pearson Education | year = 2005}}</ref> It is used to summarize information about the reactions of metals with [[acid (chemistry)|acids]] and [[water]], [[single displacement reaction]]s and the extraction of [[metals]] from their [[ore]]s.<ref>{{Cite web |title=Metal extraction and the reactivity series - The reactivity series of metals - GCSE Chemistry (Single Science) Revision - WJEC |url=https://www.bbc.co.uk/bitesize/guides/z6c26yc/revision/1 |access-date=2023-03-24 |website=BBC Bitesize |language=en-GB}}</ref>

==Table==
{| class = "Wikitable"

! Metal !! Ion !! Reactivity !! Extraction
|-
| style="background: #ffebd2" | [[Caesium]]&nbsp;Cs<!--Please don't add francium. Francium is very heavy, and so its electrons move fast enough that relativity must be considered. The end result is that the 7s electrons are stabilized, enough that Fr is probably actually LESS reactive than Cs! But nothing is known for sure.-->
| style="background: #ffebd2" | Cs<sup>+</sup>
| rowspan=8 style="background: #ffebd2" align=center | reacts with cold water
| rowspan=11 style="background: #ffebd2" align=center| [[Electrolysis]] (a.k.a. electrolytic refining)
|-
| style="background: #ffebd2" | [[Rubidium]]&nbsp;Rb
| style="background: #ffebd2" | Rb<sup>+</sup>
|-
| style="background: #ffebd2" | [[Potassium]]&nbsp;K
| style="background: #ffebd2" | K<sup>+</sup>
|-
| style="background: #ffebd2" | [[Sodium]]&nbsp;Na
| style="background: #ffebd2" | Na<sup>+</sup>
|-
| style="background: #ffebd2" | [[Lithium]]&nbsp;Li
| style="background: #ffebd2" | Li<sup>+</sup>
|-
| style="background: #ffebd2" | [[Barium]]&nbsp;Ba
| style="background: #ffebd2" | Ba<sup>2+</sup>
|-
| style="background: #ffebd2" | [[Strontium]]&nbsp;Sr
| style="background: #ffebd2" | Sr<sup>2+</sup>
|-
| style="background: #ffebd2" | [[Calcium]]&nbsp;Ca
| style="background: #ffebd2" | Ca<sup>2+</sup>
|-
| style="background: #ffeeff" | [[Magnesium]]&nbsp;Mg
| style="background: #ffeeff" | Mg<sup>2+</sup>
| rowspan=1 style="background: #ffeeff" align=center | reacts very slowly with cold water, but rapidly<br />in boiling water, and very vigorously with [[acid]]s
|-
| style="background: #ffffe6" | [[Beryllium]]&nbsp;Be
| style="background: #ffffe6" | Be<sup>2+</sup>
| rowspan=2 style="background: #ffffe6" align=center | reacts with acids and steam
|-
| style="background: #ffffe6" | [[Aluminium]]&nbsp;Al
| style="background: #ffffe6" | Al<sup>3+</sup>
|-

| style="background: #ffffe6" | [[Manganese]]&nbsp;Mn
| style="background: #ffffe6" | Mn<sup>2+</sup>
| rowspan=9 style="background: #ffffe6" align=center | reacts with [[acid]]s; very poor reaction with steam
| rowspan=2 style="background: #ffffe6" align=center | [[smelting]] with [[coke (fuel)|coke]]
|-
| style="background: #ffffe6" | [[Zinc]]&nbsp;Zn
| style="background: #ffffe6" | Zn<sup>2+</sup>
|-
| style="background: #ffffe6" | [[Chromium]]&nbsp;Cr
| style="background: #ffffe6" | Cr<sup>3+</sup> 
| rowspan=1 style="background: #ffeeff" align=center | [[aluminothermic reaction]]
|-
| style="background: #ffffe6" | [[Iron]]&nbsp;Fe
| style="background: #ffffe6" | Fe<sup>2+</sup>
| rowspan=6 style="background: #ffffe6" align=center | [[smelting]] with [[coke (fuel)|coke]]
|-
| style="background: #ffffe6" | [[Cadmium]]&nbsp;Cd
| style="background: #ffffe6" | Cd<sup>2+</sup>
|-
| style="background: #ffffe6" | [[Cobalt]]&nbsp;Co
| style="background: #ffffe6" | Co<sup>2+</sup>
|-
| style="background: #ffffe6" | [[Nickel]]&nbsp;Ni
| style="background: #ffffe6" | Ni<sup>2+</sup>
|-
| style="background: #ffffe6" | [[Tin]]&nbsp;Sn
| style="background: #ffffe6" | Sn<sup>2+</sup>
|-
| style="background: #ffffe6" | [[Lead]]&nbsp;Pb
| style="background: #ffffe6" | Pb<sup>2+</sup>
|-
| style="background: #cdcdcd" | [[Antimony]]&nbsp;Sb
| style="background: #cdcdcd" | Sb<sup>3+</sup>
| rowspan=2 style="background: #cdcdcd" align=center | may react with some strong [[oxidizing acid]]s
| rowspan=10 style="background: #cdcdcd" align=center | heat or physical extraction
|-
| style="background: #cdcdcd" | [[Bismuth]]&nbsp;Bi
| style="background: #cdcdcd" | Bi<sup>3+</sup>
|-
| style="background: #cdcdcd" | [[Copper]]&nbsp;Cu
| style="background: #cdcdcd" | Cu<sup>2+</sup>
| style="background: #ffffe6" align=center | reacts slowly with air
|-
| style="background: #cdcdcd"  | [[Tungsten]]&nbsp;W
| style="background: #cdcdcd" | W<sup>3+</sup>{{Citation needed|date=November 2024}}
| rowspan=7 style="background: #cdcdcd" align=center | may react with some strong [[oxidizing acid]]s
|-
| style="background: #cdcdcd" | [[Mercury (element)|Mercury]]&nbsp;Hg
| style="background: #cdcdcd" | Hg<sup>2+</sup>
|-
| style="background: #cdcdcd" | [[Silver]]&nbsp;Ag
| style="background: #cdcdcd" | Ag<sup>+</sup>
|- 
| style="background: #cdcdcd" | [[Gold]]&nbsp;Au
| style="background: #cdcdcd" | Au<sup>3+</sup><ref
name=":0">{{Webarchive|url=https://web.archive.org/web/20190507084512/http://www.cod.edu/people/faculty/jarman/richenda/1551_hons_materials/Activity%20series.htm|date=May 7 2019|title=Activity series}}</ref><ref>{{cite book|last=Wulsberg|first=Gary|year=2000|title=Inorganic Chemistry|url=https://books.google.com/books?id=hpWzxTnQH14C&pg=PA249|page=294|isbn=9781891389016}}</ref>
|- 
| style="background: #cdcdcd" | [[Platinum]]&nbsp;Pt

| style="background: #cdcdcd" | Pt<sup>4+</sup>
|}
<!--This is not the electrochemical series, but Gold's oxidation potential is more than half a volt higher than Platinum's. It is thermodynamicaly favourable for Pt to form PtO in air, and then PtO2; but Au won't form oxides spontaneously. Pt is used in crucibles etc, but this is due to its better mp/mechanical properties!-->

Going from the bottom to the top of the table the metals:
* increase in reactivity;
* lose electrons ([[Redox|oxidize]]) more readily to form positive ions;
* corrode or tarnish more readily;
* require more energy (and different methods) to be isolated from their compounds;
* become stronger [[reducing agent]]s ([[electron]] donors).

== Defining reactions ==

There is no unique and fully consistent way to define the reactivity series, but it is common to use the three types of reaction listed below, many of which can be performed in a high-school laboratory (at least as demonstrations).<ref name=":0" />

=== Reaction with water and acids ===

The most reactive metals, such as [[sodium]], will react with cold water to produce [[hydrogen]] and the metal [[hydroxide]]:

:2 Na (s) + 2 H<sub>2</sub>O (l) →2 NaOH (aq) + H<sub>2</sub> (g)

Metals in the middle of the reactivity series, such as [[iron]], will react with acids such as [[sulfuric acid]] (but not water at normal temperatures) to give hydrogen and a metal [[salt (chemistry)|salt]], such as [[iron(II) sulfate]]:

:Fe (s) + H<sub>2</sub>SO<sub>4</sub> (l) → FeSO<sub>4</sub> (aq) + H<sub>2</sub> (g)

There is some ambiguity at the borderlines between the groups. [[Magnesium]], [[aluminium]] and [[zinc]] ''can'' react with water, but the reaction is usually very slow unless the metal samples are specially prepared to remove the surface [[passivation layer]] of oxide which protects the rest of the metal. [[Copper]] and [[silver]] will react with [[nitric acid]]; but because nitric acid is an [[oxidizing acid]], the oxidizing agent is not the H<sup>+</sup> ion as in normal acids, but the NO<sub>3</sub><sup>−</sup> ion.

== Comparison with standard electrode potentials ==
The reactivity series is sometimes quoted in the strict reverse order of [[standard electrode potential]]s, when it is also known as the "[[electrochemical series]]".<ref>{{Webarchive|url=https://web.archive.org/web/20220224075029/https://www.primefan.ru/stuff/chem/back2019.png|date=20220224|title=Periodic table poster}} by A. V. Kulsha and T. A. Kolevich gives: {{cquote|[[lithium|Li]] > [[caesium|Cs]] > [[rubidium|Rb]] > [[potassium|K]] > [[barium|Ba]] > [[strontium|Sr]] > [[calcium|Ca]] > [[sodium|Na]] > [[lanthanum|La]] > [[yttrium|Y]] > [[magnesium|Mg]] > [[cerium|Ce]] > [[scandium|Sc]] > [[beryllium|Be]] > [[aluminium|Al]] > [[titanium|Ti]] > [[manganese|Mn]] > [[vanadium|V]] > [[chromium|Cr]] > [[zinc|Zn]] > [[gallium|Ga]] > [[iron|Fe]] > [[cadmium|Cd]] > [[indium|In]] > [[thallium|Tl]] > [[cobalt|Co]] > [[nickel|Ni]] > [[tin|Sn]] > [[lead|Pb]] > ([[hydrogen|H]]) > [[antimony|Sb]] > [[bismuth|Bi]] > [[copper|Cu]] > [[polonium|Po]] > [[ruthenium|Ru]] > [[rhodium|Rh]] > [[silver|Ag]] > [[mercury (element)|Hg]] > [[palladium|Pd]] > [[iridium|Ir]] > [[platinum|Pt]] > [[gold|Au]]}}</ref>

The following list includes the metallic elements of the first six periods. It is mostly based on tables provided by [[NIST]].<ref>[https://www.nist.gov/system/files/documents/2019/04/02/jpcrd355.pdf Standard Electrode Potentials and Temperature Coefficients in Water at 298.15 K], Steven G. Bratsch (NIST)</ref><ref>For antimony: [http://www.dactari.toxcea.org/Local/dactari/dir/pdf/default/Sb.pdf Antimony - Physico-chemical properties - DACTARI]</ref> However, not all sources give the same values: there are some differences between the precise values given by NIST and the [[CRC Handbook of Chemistry and Physics]]. In the first six periods this does not make a difference to the relative order, but in the seventh period it does, so the seventh-period elements have been excluded. (In any case, the typical oxidation states for the most accessible seventh-period elements [[thorium]] and [[uranium]] are too high to allow a direct comparison.)<ref name="CRC">{{RubberBible87th}}</ref>

Hydrogen has been included as a benchmark, although it is not a metal. Borderline [[germanium]], [[antimony]], and [[astatine]] have been included. Some other elements in the middle of the 4d and 5d rows have been omitted (Zr–Tc, Hf–Os) when their simple cations are too highly charged or of rather doubtful existence. Greyed-out rows indicate values based on estimation rather than experiment.
{| class="wikitable"
|-
! ''[[Atomic number|Z]]''
! Sym
! Element
! Reaction
! E° (V)
|-
| 3
| Li
| [[lithium]]
| Li<sup>+</sup> + e<sup>−</sup> → Li
| −3.04
|-
| 55
| Cs
| [[caesium]]
| Cs<sup>+</sup> + e<sup>−</sup> → Cs
| −3.03
|-
| 37
| Rb
| [[rubidium]]
| Rb<sup>+</sup> + e<sup>−</sup> → Rb
| −2.94
|-
| 19
| K
| [[potassium]]
| K<sup>+</sup> + e<sup>−</sup> → K
| −2.94
|-
| 56
| Ba
| [[barium]]
| Ba<sup>2+</sup> + 2 e<sup>−</sup> → Ba
| −2.91
|-
| 38
| Sr
| [[strontium]]
| Sr<sup>2+</sup> + 2 e<sup>−</sup> → Sr
| −2.90
|-
| 20
| Ca
| [[calcium]]
| Ca<sup>2+</sup> + 2 e<sup>−</sup> → Ca
| −2.87
|-
| 11
| Na
| [[sodium]]
| Na<sup>+</sup> + e<sup>−</sup> → Na
| −2.71
|-
| 57
| La
| [[lanthanum]]
| La<sup>3+</sup> + 3 e<sup>−</sup> → La
| −2.38
|-
| 39
| Y
| [[yttrium]]
| Y<sup>3+</sup> + 3 e<sup>−</sup> → Y
| −2.38
|-
| 12
| Mg
| [[magnesium]]
| Mg<sup>2+</sup> + 2 e<sup>−</sup> → Mg
| −2.36
|-
| 59
| Pr
| [[praseodymium]]
| Pr<sup>3+</sup> + 3 e<sup>−</sup> → Pr
| −2.35
|-
| 58
| Ce
| [[cerium]]
| Ce<sup>3+</sup> + 3 e<sup>−</sup> → Ce
| −2.34
|-
| 68
| Er
| [[erbium]]
| Er<sup>3+</sup> + 3 e<sup>−</sup> → Er
| −2.33
|-
| 67
| Ho
| [[holmium]]
| Ho<sup>3+</sup> + 3 e<sup>−</sup> → Ho
| −2.33
|-
| 60
| Nd
| [[neodymium]]
| Nd<sup>3+</sup> + 3 e<sup>−</sup> → Nd
| −2.32
|-
| 69
| Tm
| [[thulium]]
| Tm<sup>3+</sup> + 3 e<sup>−</sup> → Tm
| −2.32
|-
| 62
| Sm
| [[samarium]]
| Sm<sup>3+</sup> + 3 e<sup>−</sup> → Sm
| −2.30
|- bgcolor=#e8e8e8
| 61
| Pm
| [[promethium]]
| Pm<sup>3+</sup> + 3 e<sup>−</sup> → Pm
| −2.30
|-
| 66
| Dy
| [[dysprosium]]
| Dy<sup>3+</sup> + 3 e<sup>−</sup> → Dy
| −2.29
|-
| 71
| Lu
| [[lutetium]]
| Lu<sup>3+</sup> + 3 e<sup>−</sup> → Lu
| −2.28
|-
| 65
| Tb
| [[terbium]]
| Tb<sup>3+</sup> + 3 e<sup>−</sup> → Tb
| −2.28
|-
| 64
| Gd
| [[gadolinium]]
| Gd<sup>3+</sup> + 3 e<sup>−</sup> → Gd
| −2.28
|-
| 70
| Yb
| [[ytterbium]]
| Yb<sup>3+</sup> + 3 e<sup>−</sup> → Yb
| −2.19
|-
| 21
| Sc
| [[scandium]]
| Sc<sup>3+</sup> + 3 e<sup>−</sup> → Sc
| −2.09
|-
| 63
| Eu
| [[europium]]
| Eu<sup>3+</sup> + 3 e<sup>−</sup> → Eu
| −1.99
|-
| 4
| Be
| [[beryllium]]
| Be<sup>2+</sup> + 2 e<sup>−</sup> → Be
| −1.97
|-
| 13
| Al
| [[aluminium]]
| Al<sup>3+</sup> + 3 e<sup>−</sup> → Al
| −1.68
|-
| 22
| Ti
| [[titanium]]
| Ti<sup>3+</sup> + 3 e<sup>−</sup> → Ti
| −1.37
|-
| 25
| Mn
| [[manganese]]
| Mn<sup>2+</sup> + 2 e<sup>−</sup> → Mn
| −1.18
|-
| 23
| V
| [[vanadium]]
| V<sup>2+</sup> + 2 e<sup>−</sup> → V
| −1.12
|-
| 24
| Cr
| [[chromium]]
| Cr<sup>2+</sup> + 2 e<sup>−</sup> → Cr
| −0.89
|-
| 30
| Zn
| [[zinc]]
| Zn<sup>2+</sup> + 2 e<sup>−</sup> → Zn
| −0.76
|-
| 31
| Ga
| [[gallium]]
| Ga<sup>3+</sup> + 3 e<sup>−</sup> → Ga
| −0.55
|-
| 26
| Fe
| [[iron]]
| Fe<sup>2+</sup> + 2 e<sup>−</sup> → Fe
| −0.44
|-
| 48
| Cd
| [[cadmium]]
| Cd<sup>2+</sup> + 2 e<sup>−</sup> → Cd
| −0.40
|-
| 49
| In
| [[indium]]
| In<sup>3+</sup> + 3 e<sup>−</sup> → In
| −0.34
|-
| 81
| Tl
| [[thallium]]
| Tl<sup>+</sup> + e<sup>−</sup> → Tl
| −0.34
|-
| 27
| Co
| [[cobalt]]
| Co<sup>2+</sup> + 2 e<sup>−</sup> → Co
| −0.28
|-
| 28
| Ni
| [[nickel]]
| Ni<sup>2+</sup> + 2 e<sup>−</sup> → Ni
| −0.24
|-
| 50
| Sn
| [[tin]]
| Sn<sup>2+</sup> + 2 e<sup>−</sup> → Sn
| −0.14
|-
| 82
| Pb
| [[lead]]
| Pb<sup>2+</sup> + 2 e<sup>−</sup> → Pb
| −0.13
|- bgcolor=#ffcccc
| 1
| H
| [[hydrogen]]
| 2 H<sup>+</sup> + 2 e<sup>−</sup> → H<sub>2</sub>
| 0.00
|- bgcolor=#e8e8e8
| 32
| Ge
| [[germanium]]
| Ge<sup>2+</sup> + 2 e<sup>−</sup> → Ge
| +0.1
|- bgcolor=#e8e8e8
| 51
| Sb
| [[antimony]]
| Sb<sup>3+</sup> + 3 e<sup>−</sup> → Sb
| +0.15
|-
| 83
| Bi
| [[bismuth]]
| Bi<sup>3+</sup> + 3 e<sup>−</sup> → Bi
| +0.31
|-
| 29
| Cu
| [[copper]]
| Cu<sup>2+</sup> + 2 e<sup>−</sup> → Cu
| +0.34
|- bgcolor=#e8e8e8
| 84
| Po
| [[polonium]]
| Po<sup>2+</sup> + 2 e<sup>−</sup> → Po
| +0.6
|- bgcolor=#e8e8e8
| 44
| Ru
| [[ruthenium]]
| Ru<sup>3+</sup> + 3 e<sup>−</sup> → Ru
| +0.60
|-
| 45
| Rh
| [[rhodium]]
| Rh<sup>3+</sup> + 3 e<sup>−</sup> → Rh
| +0.76
|-
| 47
| Ag
| [[silver]]
| Ag<sup>+</sup> + e<sup>−</sup> → Ag
| +0.80
|-
| 80
| Hg
| [[mercury (element)|mercury]]
| Hg<sup>2+</sup> + 2 e<sup>−</sup> → Hg
| +0.85
|-
| 46
| Pd
| [[palladium]]
| Pd<sup>2+</sup> + 2 e<sup>−</sup> → Pd
| +0.92
|- bgcolor=#e8e8e8
| 77
| Ir
| [[iridium]]
| Ir<sup>3+</sup> + 3 e<sup>−</sup> → Ir
| +1.0
|- bgcolor=#e8e8e8
| 85
| At
| [[astatine]]
| At<sup>+</sup> + e<sup>−</sup> → At
| +1.0
|-
| 78
| Pt
| [[platinum]]
| Pt<sup>2+</sup> + 2 e<sup>−</sup> → Pt
| +1.18
|- bgcolor=#e8e8e8
| 79
| Au
| [[gold]]
| Au<sup>3+</sup> + 3 e<sup>−</sup> → Au
| +1.50
|}

The positions of [[lithium]] and [[sodium]] are changed on such a series.

Standard electrode potentials offer a quantitative measure of the power of a reducing agent, rather than the qualitative considerations of other reactive series. However, they are only valid for ''standard'' conditions: in particular, they only apply to reactions in aqueous solution. Even with this proviso, the electrode potentials of lithium and sodium – and hence their positions in the electrochemical series – appear anomalous. The order of reactivity, as shown by the vigour of the reaction with water or the speed at which the metal surface tarnishes in air, appears to be
:Cs > K > Na > Li > alkaline earth metals,
i.e., alkali metals > alkaline earth metals,

the same as the reverse order of the (gas-phase) [[Ionization energy|ionization energies]]. This is borne out by the extraction of metallic lithium by the electrolysis of a [[eutectic]] mixture of [[lithium chloride]] and [[potassium chloride]]: lithium metal is formed at the cathode, not potassium.<ref name="G&E">{{Greenwood&Earnshaw1st|pages=82–87}}</ref>

==Comparison with electronegativity values==
[[File:Periodic table extract metal EN values.png|thumb|upright=1.75]]

The image shows a periodic table extract with the [[electronegativity]] values of metals.<ref>{{cite book |last1=Aylward |first1=G |last2=Findlay |first2=T |last3= |first3=| date=2008 |title=SI Chemical Data |edition=6|location= Milton, Queensland|publisher= John Wiley & Sons|page= 126|isbn=978-0-470-81638-7}}</ref>

Wulfsberg<ref>{{cite book |last1= Wulfsberg|first1=G |last2= |first2= |last3= |first3=| date=2018 |title= Foundations of Inorganic Chemistry|location= Mill Valley|publisher=University Science Books |page=319 |isbn=978-1-891389-95-5}}</ref> distinguishes:<br> {{legend inline|#FF9999}} very electropositive metals with electronegativity values below 1.4<br>
{{legend inline|white}} electropositive metals with values between 1.4 and 1.9; and<br>
{{legend inline|#99CCFF}} electronegative metals with values between 1.9 and 2.54.

From the image, the group 1–2 metals and the [[lanthanide]]s and [[actinide]]s are very electropositive to electropositive; the [[transition metal]]s in groups 3 to 12 are very electropositive to electronegative; and the [[post-transition metal]]s are electropositive to electronegative. The [[noble metal]]s, inside the dashed border (as a subset of the transition metals) are very electronegative.

==See also==
* [[Reactivity (chemistry)]], which discusses the inconsistent way that the term 'reactivity' is used in chemistry.

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20040508085524/https://www.sciencenet.org.uk/database/chem/industrial/c00109b.html Science Line Chemistry]

[[Category:Inorganic chemistry]]