Anion refers to an ion whose atom obtains one or several electrons due to external action, so that the number of its outermost electrons reaches a stable structure.Anions are negatively charged ions. The number of nuclear charges=the number of protons<the number of extranuclear electrons. The number of negative charges carried is equal to the number of electrons obtained by atoms.
The charged particles formed after atoms lose or gain electrons are called ions, such as sodium ion Na+。The charged atomic group is also called "ion", such as sulfate ion.Some molecules can also form ions under special circumstances.[1]
Ions with one or more negative charges are called "anions".Many anions are stable structures in which atoms attract one or more electrons from the outside due to their own attraction, so that the number of the outermost electrons reaches 8 or 2.The smaller the radius of an atom, the stronger its ability to absorb electrons, the easier it is to form anions, and the stronger its non-metallic properties.The electrons with more than 4 electrons in the outermost layer of the atom are easy to form anions (non-metallic substances have negative valence, and anions are represented by the symbol "-"). Common anions are chloride ion Cl-, sulfur ion S2-, hydroxyl OH-Etc.
Simple anion
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name
chemical formula
combined term
Arsenic ion
As3−
Arsenide
Azide ion
N3−
Azide
Bromine ion
Br−
Bromide
Chloride ion
Cl−
chloride
Fluoride ion
F−
fluoride
Hydrogen anion
H−
hydride
Iodine ion
I−
Iodide
Nitrogen ion
N3−
nitrides
Oxyion
O2−
oxide
Phosphorus ion
P3−
Phosphide
Sulfur ion
S2−
sulfide
Peroxide ion
Otwo2−
peroxide
Oxyacid radical
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name
chemical formula
combined term
Arsenate ion
AsOfour3−
Arsenate
Arsenite ion
AsOthree3−
Arsenite
Borate ion
BOthree3−
borate
Bromate ion
BrOthree−
Bromate
Hypobromate ion
BrO−
Hypobromate
carbonate ion
COthree2−
carbonate
Bicarbonate ion
HCOthree−
Bicarbonate
Hydroxyl ion
OH−
hydroxide
Chlorate ion
ClOthree−
Chlorate
Perchlorate ion
ClOfour−
Perchlorate
Chlorite ion
ClOtwo−
Chlorite
Hypochlorite ion
ClO−
Hypochlorite
Chromate ion
CrOfour2−
chromate
Dichromate ion
CrtwoOseven2−
Dichromate
iodate ion
IOthree−
Iodate
Nitrate ion
NOthree−
Nitrate
Nitrite ion
NOtwo−
nitrite
Phosphate ion
POfour3−
phosphate
Phosphite ion
HPOthree2−
Phosphite
Monohydrogen phosphate ion
HPOfour2−
Monohydrogen phosphate
Dihydrogen phosphate ion
HtwoPOfour−
Dihydrogen phosphate
Manganate ion
MnOfour2−
Manganate
Permanganate ion
MnOfour−
permanganate
Sulfate ion
SOfour2−
sulfate
Thiosulfate ion
StwoOthree2−
Thiosulfate
Bisulfate ion
HSOfour−
Bisulfate
Sulfite ion
SOthree2−
Sulfite
Bisulfite ion
HSOthree−
Bisulfite
Persulfate ion
StwoOeight2−
Persulfate
Silicate ion
SiOfour4−
silicate
Metasilicate ion
SiOthree2−
Metasilicate
Aluminosilicate ion
AlSiOfour−
Aluminosilicate
Organic acid radical ion
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name
chemical formula
combined term
Acetate ion
CtwoHthreeOtwo−
Acetate
Formate ion
HCOtwo−
Formate
Oxalate ion
CtwoOfour2−
oxalate
Oxalate hydrogen ion
HCtwoOfour−
Oxalate
Other anions
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name
chemical formula
combined term
Hydrogen sulfide ion
HS−
Hydrogen sulfide
Tellurium ion
Te2−
Telluride
Amino anion
NHtwo−
Amino salt
Cyanate ion
OCN−
Cyanate
Thiocyanate ion
SCN−
Thiocyanate
Cyanogen ion
CN−
cyanide
Common color of ions
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name
chemical formula
colour
Permanganate ion
MnOfour-
violet
Manganate ion
MnOfour2-
green
Chromate ion
CrOfour2-
yellow
Dichromate ion
CrtwoOseven2-
orange
Bromine ion
Br-
canary yellow
Anion experiment
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Experiment purpose
Be familiar with the properties of common anions
Master the separation methods of common anions
Experimental principle
There are 13 common anions as follows: SOfour2-、SiOthree2-、POfour3-、COthree2-、SOthree2-、StwoOthree2-、S2-、Cl-、Br-、I-、NO3-、NOtwo-、Ac-
In anions, some are easy to decompose in case of acid, and some can not coexist with each other due to oxidation and reduction.Therefore, anion analysis has the following two characteristics:
Anions are easy to change in the analysis process, and it is not easy to carry out systematic analysis with various procedures.
There are few opportunities for anions to coexist with each other, and there are many specific reactions available, which may require separate analysis.
In the analysis of anions, separate analysis method is mainly used. Only when some anions interfere with each other during identification, separation method can be properly adopted.However, the separate analysis method is not to test all the studied ions one by one, but to eliminate the anions that certainly do not exist through preliminary experiments, and then to determine the possible anions one by one.
Preliminary experiment
1 Sedimentation test
(1) And BaCltwoReaction of
Drop SO into 13 centrifuge tubes respectivelyfour2-、SiOthree2-、 POfour3-、SOthree2-、 COthree2-、 StwoOthree2-、S2-、Cl-、Br-、I-、NOthree-, NO2 -, Ac -, two drops each, and then one drop of 0.5M BaCl2.
Reaction equation:
1) Ba2++ SOfour2-=BaSO4 ↓ (white)
2) Ba2++ SiOthree2-=BaSiO3 ↓ (white)
BaSiOthree+2HCl=HtwoSiOthree↓ (colloidal)+BaCltwo
3) 3 Ba2++2 POfour3-=Ba3(POfour)two↓ (white)
Bathree(POfour)two+3 HCl= BaCltwo+HthreePOfour
4) Ba2++ COthree2-=BaCOthree↓ (white)
BaCOthree+2 HCl= BaCltwo+HtwoO+COtwo↑
5) Ba2++ SOthree2-=BaSOthree↓ (white)
BaSOthree+2HCl= BaCltwo+HtwoO+SOtwo↑
6) Ba2++ StwoOthree2-=BaStwoOthree↓ (white)
BaStwoOthree+2 HCl= BaCltwo+HtwoO+SOtwo↑+S↓
And S2-、Br-、I-、NO3-、NO2-、Ac-Add BaCl intwoNo phenomenon after.
And AgNOthreeReaction of
Reaction equation:
7) 2Ag++ SOfour2-=AgtwoSOfour↓ (white)
8)2Ag++ SiOthree2-=AgtwoSiOthree↓ (white)
9)3 Ag++ POfour3-=AgthreePOfour↓ (yellow)
10)2Ag++ COthree2-=AgtwoCOthree↓ (white)
11)2Ag++ SOthree2-=AgtwoSOthree↓ (yellow)
12)2Ag++ 2S2-=AgtwoS ↓ (black)
13)Ag++ Cl-=AgCl ↓ (white)
14)Ag++ Br-=AgBr ↓ (yellow)
15)Ag++ I-=AgI ↓ (yellow)
Other ions such as NOthree-、NOtwo-、Ac-No obvious phenomenon.
2 Volatility test
Ion to be tested: SOthree2-、 COthree2-、 StwoOthree2-、S2-、NOtwo-
Observing BaStwoOthreeDuring precipitation, if there is no precipitation, friction the test tube wall with glass rod to accelerate precipitation generation.
Pay attention to AgtwoStwoOthreeThe color change of oxidative decomposition in air.
During the reduction test, attention must be paid to the added oxidant KMnOfourAnd ItwoThe amount of starch must be small, because the concentration of anions is very low.If the amount of oxidant is large, the color change of oxidant is not easy to see.