Chemical tie

1) Thing comes defined chemical tie:

Attractive forces between atoms that turn out particularly intense to allow the formation of a stable and individualistic aggregate like a distinguished entity.

THEORY OF THE VALENCE TIE

2) What is the valence:

It is the number of ties that a data atom exercises towards other atoms of one molecule. There are atoms that have a single valence and atoms that of it they have more than and changes to second of the compound in which it is found. The reason of that is from searching itself in the fact that in some case can enter to make part of the tie not only electrons of the more external layer but also those of a layer leggermente more inside with which modest difference of energy is one.

 

3) What is one structure formula:

It is a graphical representation of a compound in which the symbols of single making atoms part of the compound are interconnected through indicating hyphens the enforced ties, a double hyphen indicates a double tie.

 

4) What is the double ties and triple and which elements can create them:

The metals of 2° the period ad.eccezione.del Fluorine cannot put in common with an other atom more than one brace than electrons creating therefore a double tie.

 

5) What is the meaning for structural isomers:

They are composed isomers 2 in whose molecule the atoms are concatena you in various way.

 

6) Thing pushes more atoms to tie itself together:

They try to catch up a stable configuration that can more be that one of the octet or also, said expansion of the octet . The criterion is however always that one of the minimal energy:

to) the energy it upgrades them decreases two atoms as isolates approach infatti to you becomes much great but with sign negative.

b) the repulsion between present electrons in the two Ionian ones increases these as is approached

From an energetic point of view the turning out molecule is stabler of the system formed from 2 atoms isolates to you.

 

7) Describe the limit and rule octet its:

All the atoms stretch to catch up a stable configuration correspondent to the shell more external suit, that it can happen or for cession of electrons in excess or for electron purchase until the configuration of the noble gas. The limit is that such rule is worth only for the elements of 2° the period in how much for they the gap of energy towards the third shell is much elevated while for the periods succeeded to you an atom has the possibility to promote an electron pertaining to one brace to greater an energetic level and therefore this atom pu² to at least form 2 various numbers of ties.

 

8) What is the meaning for tie energy:

It is the job that must complete in order to carry at a distance infinite two neutral atoms (sees thermodynamics)

 

9) What is the meaning for tie distance:

It is the distance to which the nuclei of atoms joined from a sure tie are found.

 

10) What is the elettronegatività:

Molecule is the ability to an atom pertaining to one to attract to himself tie electrons.

In every period it increases approaching itself 7° the group while it decreases to increasing of the atomic number

 

11) Define the covalent bond:

It is a tie between 2 atoms with similar elettronegatività, which it introduces characteristic following:

a) the electrons are coupled disappear to you of 2 various atoms to create orbital a common one.

b) the electrons couples you of the single atom remains like solitary braces.

c) is realized the maximum superimposition between electronic clouds of 2 atoms.

 

12) How many types of covalenti ties can exist based on straight combining the nuclei:

2 types of tie can exist:

s ž if the zone of superimposition of the orbital ones is found along combining the nuclei

p ž if the zone of superimposition of the orbital ones is not found along combining the nuclei

 

13) What is a covalent bond to omopolare and from what it is characterized:

It is a covalent bond that settles down between equal or between dissimilar atoms in a generalized manner having atoms elettronegatività not much. It is symmetrical in the sense that the tie electrons are found distributed fairly between two atoms.

 

14) What is a polar covalent bond and from what it is characterized:

It is a covalent bond that is settled down between various atoms whose elettronegatività defers a lot. Asymmetric E' in how much the electrons will stretch to get thicker themselves towards the elettronegativo atom. In such a way the tie becomes more fort in how much is also electrostatic interaction between charges of opposite sign.

 

15) What is the dipolar moment:

Dipolar moment of a body is defined, in the electrically neutral complex, but in which the center of gravity of the loaded positive electrical workers does not coincide with that one of the negative charges, the product between the absolute value of the charges, for the distance that separates the barycentres of cariche the m = Q * r .

In a poliatomica molecule in order to calculate the dipolar moment it is necessary to calculate the vectorial sum of the dipolar moments relati to you to the single atoms that constitute it.

 

16) That tie is between the elettronegatività and the dipolar moment:

The scale of the elettronegatività of Pauling is constructed so that the difference of elettronegatività between 2 atoms corresponds at the dipolar moment of their molecule moreover a strong dipolar moment for a molecule makes us to preview that it will be center of a mostly ionic tie while a insufficient dipolar moment it will make to preview for that molecule a covalent bond us.

 

17) Describe the ionic tie:

Draft of a tie between an atom to high affinity electronic and an atom to bottom upgrades them of ionization. It is a typical tie of ionic crystals, the following and has had to the combination of effects:

 

18) Analogies between the ionic tie and the covalent bond:

The ionic tie can is considered like a polar covalent bond where but the difference of elettronegatività between two atoms therefore is elevated that pu² nearly to say itself that the elettronegativo atom tears electrons to the less elettronegativo atom, and both become Ionian.

 

19) What is the reticular energy of ionic crystals:

It is the energy difference upgrades them electrostatic between the system constituted from the 2 Ionian ones isolates and the system to you that sees the two Ionian ones in the respective positions of a crystal.

 

20) Describe the tie dative or of coordination:

It is a tie that settles down between one substance (donor) able to yield one electron brace and one substance (accepter) able to accept one electron brace, to the aim to catch up both one stable configuration.

 

21) That difference is between the tie dative and the covalent bond:

In the tie dative the tie electron brace is supplied from one only of 2 atoms while in the covalent bond, every atom supplies an electron.

 

22) Causes of the covalent bond:

to) For via of the superimposition of the two orbital every electron it can be found indifferently also in the volume of the other, that approaches the barycentres of the distributions of loads, therefore the angular moment he is inferior and with it the kinetic energy therefore totally the molecule is stabler.

b) there is a distance to which they balance the attraction between the zone of superimposition of the two orbital and nuclei. and the repulsion between the two nuclei or two electrons.

 

23) What is the orbital hybrids and to what they serve in the theory of the valence tie:

There are cases in which the external configuration of an atom it is not lend to create stable covalenti ties, like as an example for atoms with a n° equal of electrons on the more external layer. In such case in occasion of the formation of the tie they are created of orbital hybrid sayings, in how many orbital due to the superimposition of 2 simple ones, which have such characteristics to render nascituro the covalent bond stabler.

 

24) Describe the process of hybridization and consequent formation of the tie:

It articulates itself in 3 makes itself:

to) one of 2 electrons it comes immediately promoted to the orbital one ollowing.

b) the hybridization happens that consists in the creation of 2 orbital equal hybrids to leave from the combination of the orbital promoted simple and of the orbital one.

c) formation of the tie.

 

25) Describe some orbital hybrids:

The type of the orbital hybrid is tightened function of the orbital ones that generates it, some examples is:

sp ž is originated from the combination of orbital s and an orbital one p

sp² ž are originated from the combination of orbital s and 2 orbital ones p

sp³ ž are originated from the combination of orbital s and 3 orbital ones p

sp³d ž are originated from the orbital combination of s, 3 orbital p and 1 orbital one d

sp³d² ž are originated from the orbital combination of s, 3 orbital p and 2 an orbital one d

 

26) It is possible that a same atom gives place to orbital various hybrids:

, it is the case of carbon which before a 1s ² 2s ¹ 2p ³ promotes1electronfromstop passing da 1s²2s²2p² dopodichè to second of the type of atoms which it must be tied are possible the hybridizations:

sp ž acetylene C₂H₂

sp² ž ethylene C₂H₄

sp³ ž methane CH₄

 

27) What is the meaning with the term geometric isomers:

Molecule draft that beyond to having same atoms has also the same ties but with a various disposition spaces them, speaks about isomer CIS (from the same part respect to an orthogonal plan to the tie) in the case is a symmetry spaces them while respect to an orthogonal plan to the tie) in asymmetry case is spoken about isomer TRANS (from the opposite part. All this has sense in presence of double ties in how much they only renders a spin impossible that it would invalidate the meant one of CIS and TRANS.

 

28) What is the rotameri:

They are of the geometric isomers for which it can easily be passed from one to the other through a spin, the case is this in which the tie it is of type s while that is not possible for a type tie p.

 

29) What is the mesoneria resonance or:

It is a concept that is used in order to characterize the cases in which a molecule it can have more formulas than Lewis that per² are only distinguished between they for the disposition of electrons and therefore of the ties and not for the position of the nuclei of constituent atoms. The structure of molecules in such case is not some of the structures characterized from the formulas of Lewis but a hybrid of resonance between all they. In the case as an example of the benzene, such concept is the only one to explain like 3 ties can be fairly distributed on 2 of the C of the hexagonal chain.

 

30) the stability of the resonance hybrid is greater or smaller of the stability of the formulas of Lewis from which it comes:

The stability turns out greater single if all the canonical shapes have comparable stability, otherwise prevails one of they and it can be thought that the real molecule coincides with that date formula of Lewis.

 

31) What is the paramagnetism and, when a molecule is paramagnetic:

The paramagnetism is the property to endure an attraction from part of a magnetic field. A molecule is paramagnetic when it contains at least an electron not joined.

 

32) What is the diamagnetismo and, when a molecule is diamagnetic:

The diamagnetismo is the property to endure a repulsion from part of an external magnetic field. A molecule is diamagnetic when it contains alone electrons joins to you. Every molecule is diamagnetic in how much all introduces at least 2 electrons joins to you, but the presence of a single spaiato electron determines a advanced magnetic effect to the effect of all the electrons joins to you.

THEORY OF ORBITAL MOLECULAR ONES

33) Which problem of the theory of the valence tie comes shiningly resolved from the theory of orbital molecular ones:

The paramagnetic behavior of some molecules.

 

34) Which it is the difference between this theory and the theory of the valence tie:

The valence electrons more do not come to occupy single orbital the atomic ones which are overlapped in the covalent bond bens¬ occupy of orbital molecular characteristic of the every one particular molecule.

 

35) Which it is the mathematical sense of orbital molecular ones:

The wave functions are taken (which can assume are positive values you that denied you to the contrary of the density of probabilities) of orbital atomic constituent orbital the molecular one in issue, if of fà a linear combination, and if the two functions have opposite signs the result are an orbital one of antitie, otherwise an orbital one of tie is had.

 

36) What is orbital an atomic one of valence and that role has in the theory of the molecular tie:

Draft of orbital atomic the pertaining ones to a not complete shell. They are the only ones that they form, for linear combination, orbital the molecular ones, in fact if a molecular one is created orbital on the more external layer, the atoms are placed to a such distance that orbital the atomic insides cannot be created, in how much space separate to you.

 

37) What is a node for an orbital one and that relationship is with the energy of the orbital one:

It is a zone of the space in which not there is some probability to find an electron. If we see the orbital one as the orbit continuation from a harmonic wave we notice that how much more elevated it is the n° of nodes, much more elevated is the frequency of the wave and therefore much more elevated it is also the energy of same in fact and = h the v. Therefore much more they are the nodes in orbital the molecular one turning out much more elevated is the energy of the orbital one and therefore the instability, will be therefore the orbital ones of antitie to being characterizes to you from elevating n° of nodes.

 

38) That type of orbital is obtained from the combination of two orbital atomic ones 1s:

Orbital ones are obtained 2, characterize from different energetic geometries and levels to you that can accommodate both 2 electrons with spin antiparallels:

s_1S has density electronic maximum nella zone comprised between the 2 nuclei, is to an inferior energetic level on the credit side 1s and therefore turns out stabler respect to it, comes therefore defined orbital of tie. It does not have nodes.

s_1S^* has the maximum density electronic in the external zone to the 2 nuclei, is to a advanced energetic level to the 1s and unstable therefore, comes therefore defined orbital of antitie. It has nodo.a

 

39) As the n° is estimated of ties with the theory of orbital molecular ones and to what it serves:

The formula is used:

If the n° of 0 ties the molecule is equal to then it cannot exist otherwise with growing of the n° of ties it increases the force of the tie and diminishes the distance between the nuclei.

 

40) That type of orbital obtains from the combination of orbital atomic 2p_Z being z combining the nuclei?

Orbital ones are obtained 2:

s_2P stable to orbital incartata candy shape said of tie. It introduces 2 nodes.

s_2P^* unstable to shape of 2 separated barbapapà that sleep witness, is said orbital of antitie. It introduces 3 nodes.

 

41) That type of orbital is obtained from the combination of orbital atomic 2p_X being z combining the nuclei:

Orbital ones are obtained 2:

p_2P stable to shape of two ellissoidi, over and the other under to the nodal plan, is said orbital of tie

p_2P^* unstable to shape of four ellissoidi separates to you from 2 nodal plans, is said orbital of antitie.

Analogous for the combination of 2 orbital 2p_{Y .}

 

42) Thing happens when one is had biatomic molecule with having atoms orbital to considerably different energies:

3 types of orbital can be obtained:

* a stable orbital saying of tie to energy and shape much next one to that one of the elettronegativo atom, what that is identified with the fact that it attracts to himself tie electrons.

* one unstable orbital saying of antitie to energy and shape much next one to that one of the less elettronegativo atom.

* an orbital saying not tie which had to the fact that one of 2 atoms has a greater electron number regarding the other

The orbital co-existence of orbital typically similar to those of the elettronegativo atom with typically similar to those of the less elettronegativo atom, determines the ionic character of the molecule.

 

43) Which orbital ones are arranged in a tie between two various atoms:

Those having are arranged values of next energies much, which often can be orbital of various type, this as an example in hydrofluoric acid HF is explained with the fact that the H has orbital 1s the much more distant from the nucleus of how much is not distant the orbital one 1s from the nucleus of F, this why it loads with the nucleus is stronger and therefore it attracts with more force the pertaining electrons to it, which therefore will be found on orbital more low energy.

 

44) That type of orbital is obtained from the combination of orbital atomic 2s and 2p_Z :

Orbital ones are obtained 2:

s_2SP stable to shape case of guitar with in head a picciuolo, said orbital of legame.

s_2SP^* unstable to shape of one sphere and a ellissoide, orbital saying of antitie.

 

45) That type of orbital is obtained from the combination of orbital atomic 2s and 2p_X or 2p_Y :

Being various the symmetry aces, molecular one is not formed some orbital and the atoms remain in their orbital atomic ones of departure.

 

46) Thing indicates notation (p_2P^*)²

It indicates the presence of 2 electrons in the orbital one p_2P^* .

 

47) the concepts of the hybridization and the resonance are only worth for the theory of the tie of valence or also for the theory of orbital molecular ones:

Which are worth for both the theories di.le can be considered like accessories.