One of the key con­cepts the al­lows united state to de­scribe the ox­i­da­tion and also re­duc­tion prop­er­ties of mol­e­cules is the ox­i­da­tion state. This is only an aux­il­iary quan­ti­ty: the does not de­scribe the true fee on every of the atoms in the mol­e­cule, yet helps to get an idea exactly how the giv­ing up and ac­cep­tance of elec­trons takes location in ox­i­da­tion and also re­duc­tion re­ac­tions. Over there is a cer­tain an approach that helps us to cal­cu­late cor­rect­ly the ox­i­da­tion states for each atom.

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How come de­ter­mine the ox­i­da­tion state in a sim­ple sub­stance

Sub­stances are referred to as sim­ple i m sorry con­sist of atoms of the exact same kind. For ex­am­ple, sim­ple sub­stances in­clude oxy­gen (O₂), hy­dro­gen (H₂), sodi­um (Na), beryl­li­um (Be), io­dine (I₂), ozone (O₃) and oth­ers.

Each of this sub­stances has a zero ox­i­da­tion state. This can be ex­plained by the fact that the elec­trons in mol­e­cules that this type do not change any­where. In di­atom­ic mol­e­cules con­sist­ing of atoms of one el­e­ment, a co­va­lent non-po­lar bond is re­al­ized (Cl-Cl; H-H): together bond­ed atoms are equal, the dis­place­ment the elec­tron den­si­ty to any oth­er atom is no ob­served, and also so the move­ment of elec­trons does no take place. In monoatom­ic mol­e­cules (for ex­am­ple he­li­um He, Ar­gon Ar), the ox­i­da­tion state is also zero.

How come de­ter­mine ox­i­da­tion states in com­plex sub­stances

Sub­stances are referred to as com­plex i beg your pardon con­sist of two or more types of atoms.


For ex­am­ple, ta­ble salt NaCl is a com­plex (or bi­na­ry, i.e. Con­sist­ing of atom of two types) com­pound, as it con­tains atom of dif­fer­ent elec­tron con­fig­u­ra­tions that are chem­i­cal­ly con­nect­ed to each oth­er. In this com­pounds you have the right to place the non-zero ox­i­da­tion states, together a move­ment the elec­tron den­si­ty is ob­served to the many elec­tri­cal­ly neg­a­tive el­e­ment. In sodi­um chlo­ride, the elec­tri­cal neg­a­tiv­i­ty is high­er in chlo­rine (this non-met­al is a strong ox­i­diz­er, and so its elec­tri­cal neg­a­tiv­i­ty is much high­er 보다 sodi­um, i beg your pardon is a re­duc­er). The ox­i­da­tion state that sodi­um is +1, and also the ox­i­da­tion state the chlo­rine is -1.

To es­tab­lish the cor­rect ox­i­da­tion state on one atom in a com­pound, we may use the fol­low­ing rules.

1. The ox­i­da­tion state of oxy­gen in com­pounds is usu­al­ly -2 (an ex­cep­tion is per­ox­ide (for ex­am­ple Na₂O₂) and su­per­ox­ides (KO₂), where the ox­i­da­tion state the oxy­gen is -1 and -1/2 re­spec­tive­ly; in ozonides such together KO₃ the ox­i­da­tion state the oxy­gen is -1/3; oxy­gen only has the pos­i­tive ox­i­da­tion state that +2 in the com­pound with flu­o­rine OF₂).

2. The ox­i­da­tion state that flu­o­rine is al­ways -1.

By Giovani Rech - own work, CC BY-SA 4.0, Link

An­i­ma­tion show­ing the crys­tal struc­ture that beta-flu­o­rine

3. The max­i­mum ox­i­da­tion state of an el­e­ment is fre­quent­ly same to the num­ber that the group it is lo­cat­ed in; ex­cep­tions space oxy­gen (+2), flu­o­rine (-1), steel (+6), the sub­group that nick­el (+3, more rarely +4), and also no­ble gas­es.

4. The min­i­mum neg­a­tive ox­i­da­tion state is cal­cu­lat­ed ac­cord­ing to the for­mu­la: the num­ber that the team mi­nus 8 (in cal­cu­lat­ing the va­lence, the for­mu­la is cal­cu­lat­ed vice ver­sa – the num­ber that the team is sub­tract­ed from 8).

5. Ox­i­da­tion states of sim­ple monoatom­ic ions are equal to their charges (for ex­am­ple, Na(+) has actually both a charge of 1+ and also an ox­i­da­tion state the +1; a sim­i­lar sit­u­a­tion ex­ists through Mg(2+), F(-) etc.).

6. In non-ion­ic com­pounds, the ox­i­da­tion de­gree that hy­dro­gen is +1 (an ex­cep­tion is com­pounds through sil­i­con and ar­senic SiH₄ и AsH₃; in hy­dro­gen hy­drides hy­dro­gen likewise has a neg­a­tive ox­i­da­tion state: in NaH sodi­um has actually an ox­i­da­tion state that +1, if hy­dro­gen has an ox­i­da­tion state of -1).

7. In com­pounds that non-met­als, which carry out not con­tain hy­dro­gen or oxy­gen, the atom through the neg­a­tive ox­i­da­tion state is the one through a high­er elec­tri­cal neg­a­tiv­i­ty (it deserve to be viewed in the cor­re­spond­ing ref­er­ence ta­ble): the val­ue the the ox­i­da­tion state in this com­pounds because that a more elec­tri­cal­ly neg­a­tive non-met­al cor­re­sponds come the fee of its most wide­spread ion (in car­bon sul­fide CS₂ car­bon has the ox­i­da­tion state that +4, if sul­fur is a more elec­tri­cal­ly neg­a­tive atom, and also its many com­mon ion has actually the charge of -2.

Carbon sulfide CS₂

Ac­cord­ing to these rules, we have the right to cal­cu­late the ox­i­da­tion claims of atoms because that any mol­e­cule.

Cal­cu­lat­ing ox­i­da­tion claims in com­plex mol­e­cules

The sum­ma­ry ox­i­da­tion of a mol­e­cule must be zero, together the mol­e­cule is neu­tral.

Cal­cu­lat­ing val­ues because that el­e­ments which have the right to have sev­er­al ox­i­da­tion states

In cal­cu­lat­ing sum­ma­ry ox­i­da­tion states, at­ten­tion is al­ways paid to in­dices: in the per­chlo­ric acid mol­e­cule HClO₄ oxy­gen has actually the ox­i­da­tion state of -2. Together there are 4 oxy­gen atom in the mol­e­cule, its ox­i­da­tion state is mul­ti­plied by 4: -2*4 = -8.

This plays a duty in de­ter­min­ing ox­i­da­tion claims in el­e­ments in which this val­ue might vary. Chlo­rine has many pos­si­ble ox­i­da­tion states, for this reason the val­ue for HClO₄ might be cal­cu­lat­ed math­e­mat­i­cal­ly, through the equa­tion:

+1 + х + (-2)*4 = 0

х = +7

The ox­i­da­tion state of chlo­rine in per­chlo­ric acid is +7, as each that the 4 oxy­gen atoms have an ox­i­da­tion state that -2, this val­ue is +1 because that hy­dro­gen, and also the mol­e­cule must have actually a zero ox­i­da­tion state in this sum).

Equa­tion that ox­i­da­tion states of el­e­ments in mag­ne­sium and beryl­li­um hy­drox­ides

Magnesium hydroxide

In mag­ne­sium hy­drox­ide Mg(OH)₂ there space two hy­dro­gen atoms with an ox­i­da­tion state the +1 and two oxy­gen atoms through ox­i­da­tion claims of -2. If these ox­i­da­tion states are included tak­ing the in­dices right into ac­count, we may re­ceive the val­ue the -2: (+1)*2+(-2)*2= -2.

The ox­i­da­tion state that mag­ne­sium in the com­pound is +2 (as mag­ne­sium is a mem­ber the the sec­ond team of the pe­ri­od­ic ta­ble).

When we include the val­ues, we get zero: +2+(-2)=0.

This way that the ox­i­da­tion states have been cal­cu­lat­ed cor­rect­ly: for mag­ne­sium the val­ue is +2, for oxy­gen -2 and for hy­dro­gen +1.

All atoms in mag­ne­sium hy­drox­ide Mg(OH)₂ have actually fixed val­ues that ox­i­da­tion states, therefore this com­pound is a rather sim­ple situation for de­ter­min­ing con­di­tion­al charges in atoms.

The sit­u­a­tion v beryl­li­um hy­drox­ide Be(OH)₂ is sim­i­lar: the ox­i­da­tion state the beryl­li­um al­ways cor­re­sponds to its charge and is +2, the ox­i­da­tion state that oxy­gen of com­pounds is -2, and also of hy­dro­gen +1. If this val­ues are included tak­ing into ac­count the in­dices, we get zero:

+2 + (-2 + (+1))*2 = 0.

How the ox­i­da­tion state dif­fers from va­lence and charge

The ox­i­da­tion state, va­lence and also charge of an el­e­ment are of­ten iden­ti­cal in val­ue. Nev­er­the­less, this con­cepts have actually a dif­fer­ent mean­ing. The ox­i­da­tion state is the con­di­tion­al fee on each atom in the com­pound (it is writ­ten over each atom, and very first its al­ge­bra­ic sign need to be in­di­cat­ed, and then the nu­mer­i­cal val­ue). The ion charge is writ­ten dif­fer­ent­ly: for sim­ple ions it is also writ­ten above the el­e­ment sym­bol, but first its val­ue is in­di­cat­ed, and then the al­ge­bra­ic sign (for ex­am­ple, 2+). For com­plex ions (such as the sul­fate ion SO₄²⁻), the charge is no in­di­cat­ed over the spe­cif­ic el­e­ment, together the ox­i­da­tion state, but above the en­tire com­plex ion. Click right here to discover out much more about ox­i­da­tion states.

The charge is con­nect­ed through its ox­i­da­tion states: because that ex­am­ple in Mg(OH)₂ 2 hy­drox­yl groups are present. The fee of the OH group is al­ways (1-). Ac­cord­ing come the rules, the amount of the ox­i­da­tion states of atoms in this team should be equal to its charge (for the five group, which con­sists the oxy­gen and also hy­dro­gen, this ascendancy is ob­served, as -2+1=-1).

Giv­en the there are two OH teams in mag­ne­sium hy­drox­ide, we may say that their sum­ma­ry charge is (2-). The ox­i­da­tion state of mag­ne­sium (+2) co­in­cides with its charge (2+).

Va­lence is the abil­i­ty of atom to type a cer­tain num­ber the chem­i­cal bonds. It can only have actually a pos­i­tive val­ue. Of­ten va­lence co­in­cides v the ox­i­da­tion lev­el in its nu­mer­i­cal val­ue, yet there are also cer­tain ex­cep­tions – in ni­tric mountain HNO₃ the va­lence that ni­tro­gen is IV, however the ox­i­da­tion state is +5.


In molec­u­lar ni­tro­gen a triple bond is re­al­ized be­tween atom (so va­lence is III), but the ox­i­da­tion state is 0. Va­lence may be de­ter­mined by the struc­tural for­mu­la the the sub­stance.

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The ox­i­da­tion state dram a an essential role in record­ing the ox­i­da­tion-re­duc­tion pro­cess­es through the an approach of elec­tron bal­ances. The elec­tron bal­ance is the sim­plest an approach of record­ing the move­ment the elec­trons in a re­ac­tion, in i m sorry not genuine par­ti­cles space ex­am­ined, i m sorry ex­ist in a so­lu­tion (for ex­am­ple ions), however only atoms in com­pounds, which adjust their ox­i­da­tion states, giv­ing and also tak­ing elec­trons.