Redox reactions know how to know the valency of the elements

Catch some definite, such as o in most cases, unless it is with f, it is -2 valence, such as h, most of the time it is +1, f is always -1, na, k, li is always +1, mg, ca is always +2, and everything else is reversed;

The above problems: 1. CL can be calculated as +5 valence in the front and +4 valence in the back, which is reduced and is an oxidant; The apparent valency of C in the front is -2, and the back is +4, which rises by 6, so it is oxidized and is a reducing agent;

2. The apparent valency of c in front can be calculated as 0, followed by 4; Whereas, the o of oxygen is 0 and is followed by -2.

It should be noted that due to the particularity of C, it can present many kinds of valence, such as -2 in C3H6 and even -8 3 in C3H8, which are not real valence manifestations and can only be treated as apparent valence.

Hopefully, this rule will work for you.

For the usual inorganic compounds, it can be judged by memorizing their conventional valence, starting from some more special elements, such as CAC2 calcium carbide, in which Ca calcium is a metal element, generally only positive 2 valence, so C carbon is negative 1 valence.

For organic compounds, O-2, H+1, N-3, according to these, and molecules that are uncharged can be introduced to the valence state of C carbon (almost covering minus 4 to plus four, including 0 valence).

The above is only valid for high school chemistry).

The change in the elevated valency of an element is called an oxidation reaction; The valency of the elements is elevatedsubstance— calledReducing agent

The valency of the element is reducedVariations— calledReduction reaction；The valency of the element is reducedsubstance— calledOxidizing agent

Oxidizing agentwithReducing agentIt's all aboutreactants。After the reaction, the oxidant is reduced; The reducing agent is oxidized

For example: carbon + oxygen = carbon dioxide.

The carbon element has increased from 0 valence to positive 4 valence, yesOxidation reactions。Carbon is a substanceReducing agent, after the reaction,is oxidized

Oxygen is reduced from 0 valence to minus 2 valence, yesReduction reaction。Oxygen is a substanceOxidizing agent, after the reaction,is restored

In the redox reaction, there must be a change in valency, in which if oxygen is involved, then the oxygen is either increased or decreased, the decrease is most of the reaction, and the increase can only occur in the reaction with fluorine, because the oxidation of fluorine is stronger than that of oxygen, for example.

f2+2h2o=2hf+o2

In addition to this, the oxidation valency is reduced.

The valency of oxygen is commonly 0,-1,-2

Compounds correspond to O2, H2O2, and H2O, which are increased by oxidation and reduced by reduction.

Rise and lose oxygen, and fall back.

The valency increases, loses electrons, is oxidized, and oxidation reactions occur as a reducing agent;

The valency decreases, electrons are obtained, they are reduced, and a reduction reaction occurs, which is used as an oxidant.

Apparently speaking, the valency of an element is calculated from the chemical formula of the molecule in which the element is located, and the algebraic sum of the valency of each element of an uncharged compound is +1 valence in most cases, and -1 valence in most cases, and these fixed valencies are used to find the valency of unknown elements. For example, the water molecule H2O, because H is +1 valence, so O is -2 valence. If an element appears more than once in a molecule, the average valency of that element is actually obtained.

For example, Fe3O4, how can an iron atom lose eight-thirds of its electrons, in fact, one iron atom loses three electrons, two Tehara Sakurahashiko loses two electrons, and three iron atoms lose a total of eight electrons.

Essentially, valency reflects the electrons gained and lost by an element's atoms. Lose an electron +1 valence, gain an electron -1 valence. The specific gains and losses should be analyzed from the electronegativity and spatial structure of the molecule.

For example, the propane molecule CH3-CH2-CH3, compared with H, C has a large electronegativity, and the bonding electron pair is biased towards C, so there is a C-H bond, and C gets the valency minus 1; The electron pairs on the C-C bond are not deflected, and if there is a C-C bond, the valency of C is increased by 0; Finally, the first C in the propane molecule has three C-H bonds and one C-C bond, which adds up to the -3 valence; And the one in the middle is -2 valence.

Specifically, the atom loses or gains a few electrons to stabilize, which is related to the arrangement of the nuclear cores of the electric ridge outside the atom.

The changes in the positive valence state are basically in the transition elements, such as copper has a valent cuprous and a bivalent copper. According to the electronic arrangement, the extranuclear electrons of copper are 3d9 4s2, that is, it has two outermost electrons, both of which are lost, that is, +2 valence. But if the 3d orbital is fully filled, it is also a stable structure, and in fact the copper atom is indeed 3d10 4s1, that is, the outermost shell is an electron, which loses the +1 valence.

This is the reason why copper can show +1 price and +2 price.

The same is true of the change in the price of the negative cherry blossom song. This part of the atoms is mainly non-metallic elements. For example, N, in N2O5, +5 valence, and in NH3, -3 valence.

n There are 5 electrons outside the nucleus, and the electron configuration is 2s2 2p3, that is, in the atomic state, two of these 5 electrons are a lone pair, and the other three are odd electrons. In N2O5, all 5 electrons are involved in bonding, and the bonding electron pairs are biased towards O atoms, so N is +5 valence. In NH3, the lone pair of electrons does not participate in bonding, the three odd electrons each bond with H, and the bonding electron pair is biased towards n atoms, so N is -3 valence.

Hello! In general, the higher the valency of the element, the stronger the oxidation; The lower the valency, the stronger the reducibility.

The lowest valency has no oxidation, and the highest valency has no reducibility.

However, there may be differences in different patterns. For example, sulfite (s:+4) is soluble in water, and its reducibility in water is stronger than that of powdered s(0).

The law of valence related:

1. The unit quality is 0 price. Such as O2, H2, S, FE, C, Cu, etc.

2. H is generally +1 valence (but the metal hydride is medium-the-skin and H is -1 valence, such as NAH, CAH2, etc. are missing).

3. O is generally -2 valent (but in peroxides, O is -1 valence, such as Na2O2, H2O2, etc.).

4. The charge number of the ion = its valence number, such as CI- is -1 valence, S2- is -2 valence OH- overall is -1 valence.

5. In any substance, the algebraic sum of positive and negative valence is 0

Common valencies of common elements:

1 price: k, na, ag, h

2 valents: MG, ZN, CA, BA

3 valence: ALFE: +2, +3 valence.

cu: +1, +2 valence.

cl：-1 、+1、+3、+5、+7

s：-2、+4、+6

mn: +2, +4, +6, +7

n：-3、+1、+2、+3、+4、+5

Now let's find the undetermined valence state according to the known valence state, e.g. kclo3, k must be +1 valence, o must be -2 valence, which cl is the price? According to the algebraic sum of positive and negative valence is 0, that is, +1+5+3*(-2)=0, so CI is +5 valence.

NH4NO3: NH4+, the number of charges carried by the ion = its valency number, so NH4+ as a whole shows +1 valence, H must be +1, so how to find N in it? -3+4*1=+1, so nh4+ in n is -3 valent.

no3-, the overall -1 valence, o must be -2 valence, according to +5+3*(-2)=-1, so no3-medium n is +5 valence.

No, as long as there is a valency of the element.

When a change occurs, a redox reaction occurs.

Because, the essence of the redox reaction is that the gain and loss of electrons or the shift of common electron pairs occurs in the reaction, that is, the transfer of electrons.

Therefore, as long as there is a change in the valency of an element in the reaction, a redox reaction has occurred, and the valency of all elements does not need to change; For example: some well-known chemical reactions.

cu+fecl2==cucl2+fe

The reaction is a redox reaction, but the valency of Cl is always -1 and does not change!

No. Just change one.

For example. Fe + HCI = FeCl2 + H2 gas.

Fe acts as a reducing agent.

HCI is an oxidizing agent, so it has changed by two.