Fundamentals of General Chemistry. Terms and Problems in Tests In 2 parts. P.1. Terms and Examples in Tasks. Study guide
.pdf3 . M O L E C U L A R O R B I T A L ( М О ) T H E O R Y
3 . 1 . D i c t i o n a r y
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Antibonding MO |
Разрыхляющая МО |
Bond dissociation energy or enthalpy |
Энергия диссоциации или энталь- |
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пия связи |
Bond distance or bond length |
Длина связи |
Bond order |
Порядок связи |
Bonding МО |
Связывающая МО |
Compound |
Соединение |
Covalent bond |
Ковалентная связь |
Diamagnetic |
Диамагнитный |
Empty molecular orbital |
Свободная молекулярная орбиталь |
Heteronuclear diatomic molecule |
Гетероядерная двухатомная моле- |
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кула |
Homonuclear diatomic molecule |
Гомоядерная двухатомная молекула |
Ion |
Ион |
Isoelectronic species |
Изоэлектронные частицы |
Magnetic properties |
Магнитные свойства |
Molecular orbital МО |
Молекулярная орбиталь МО |
MOs |
Молекулярные орбитали |
Molecular orbital (МО) theory |
Теория молекулярных орбиталей |
Molecule |
Молекула |
Non-bonding |
Несвязывающая |
Nuclei |
Ядра |
Nucleus |
Ядро |
Occupied molecular orbital |
Занятая молекулярная орбиталь |
Overlap |
Перекрывание |
Pairing of electrons |
Спаривание электронов |
Paramagnetic |
Парамагнитный |
Stable |
Стабильный |
Valence atomic orbital |
Валентная атомная орбиталь |
Unpaired electrons |
Неспаренные электроны |
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3 . 2 . W o r k e d e x a m p l e s
Example 1. Construct an MO diagram for |
the F2 molecule. Write |
the ground state electronic configuration of an |
F2 molecule. Determine |
the bond order in F2. What magnetic properties does a molecule F2 have? Will the ions F2+ and F2− be diamagnetic or paramagnetic?
Answer
Molecular orbital theory can be applied to any homonuclear diatomic molecule. The ground state electronic configuration of a fluorine atom is 1s22s22p5. We can construct an MO diagram for the formation of F2 by considering the linear combination of the atomic orbitals of the two fluorine atoms. An important ground-rule of MO theory is that the number of MOs that can be formed must be equal to the number of atomic orbitals of the constituent atoms.
The interaction between the core 1s atomic orbitals can be ignored since the bonding is determined by the interaction between the valence atomic orbitals. Each F atom has four valence orbitals 2s, 2p and the number of MOs must be equal to eight. Overlap occurs between the 2s atomic orbitals of two fluorine atoms to give one (2s)-bonding MO and one*(2s)-antibonding MO.
The nuclei of F atoms are placed on the z axis. Defining these positions also defines the relative orientations of the two sets of p orbitals. Overlap occurs between the 2pz atomic orbitals of two fluorine atoms to give one (2pz)-bonding MO and one *(2pz)-antibonding MO. Two(2px)- and (2py)-bonding MOs and two *(2px)- and *(2py)-antibonding MOs are formed by the overlap of the two 2px orbitals and two 2py orbitals of the two F atoms, respectively. In F2 there are 14 valence electrons of the two F atoms and these occupy the MOs according to the rules (a) orbitals are filled in order of increasing energy, the lowest energy orbitals being filled first, (b) Hund’s rule, (c) Pauli exclusion principle. Figure show MO diagram for the formation of an F2 molecule.
The ground state electronic configuration of F2 can be written as:
(2s)2 *(2s)2 (2pz)2 (2px)2 (2py)2 *(2px)2 *(2py)2.
The bond order in F2 can be determined by using equation:
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Number of |
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Number of |
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Bond order = |
bonding electrons |
− antibonding electrons |
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АО(F) МО(F2) |
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АО(F) |
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*(2pz) |
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*(2px) |
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2p |
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*(2s) |
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2s |
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2s |
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Bond order in F2= 8 −2 6 =1.
This is molecule with a single bond.
All the electrons in F2 are paired, so the molecule of F2 is diamagnetic. The ion F2− has one more valence electron than F2 and this will occupy*(2pz)-antibonding MO. The ion F2+ has one less valence electron than F2, therefore the *(2py)-antibonding MO of F2− is occupied by only one electron. Thus, the ions F2+ and F2− will be particles with unpaired electrons and, therefore, paramagnetic.
Example 2. Show that the species N2 and [CN]− are isoelectronic.
Answer
The word isoelectronic often means the same number of valence electrons. The atoms of C, N contain four and five valence electrons, respectively. The molecule N2 possesses (5 + 5) = 10 electrons. The anion [CN]− possesses (4 + 5 + 1) = 10 electrons. Therefore, the molecule N2 and the anion [CN]− are isoelectronic.
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3 . 3 . T a s k s f o r s e l f - c o n t r o l |
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1. |
Using the MO theory, predict which a particle is diamagnetic: |
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A) O2+; |
B) N2+; |
C) O2; |
D) F2. |
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According to the MO theory, a molecule is paramagnetic: |
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А) C2; |
B) F2; |
C) N2; |
D) O2. |
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3. |
According to the MO theory, a molecule is paramagnetic: |
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А) H2; |
B) F2; |
C) C2; |
D) B2. |
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4. |
Using the MO theory, predict which a molecule is the most stable: |
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А) H2; |
B) С2; |
C) В2; |
D) Ne2. |
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5. |
According to the MO theory the bond order in О2 is: |
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A) 1; |
B) 2; |
C) 1.5; |
D) 2.5. |
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6. |
According to the MO theory the bond order in Ne2 is: |
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A) 1; |
B) 2; |
C) 0; |
D) 3. |
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According to the MO theory the bond order in С2 is: |
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A) 1; |
B) 2; |
C) 1.5; |
D) 2.5. |
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8. |
According to the MO theory the bond order in the CO molecule is: |
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А) 1; |
B) 2; |
C) 3; |
D) 4. |
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According to the MO theory, the smallest bond order in the molecule is: |
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А) C2; |
B) F2; |
C) N2; |
D) O2. |
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According to the MO theory, the largest bond order in the particle is: |
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А) H2+; |
B) H2; |
C) He2; |
D) He2+. |
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According to the MO theory, the largest bond order in the molecule is: |
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А) C2; |
B) F2; |
C) N2; |
D) O2. |
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The heteronuclear particle, which is isoelectronic to the N2 molecule, is: |
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А) C2; |
B) СО; |
C) NO−; |
D) NO. |
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13. The MO diagram |
АО МО АО |
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1s |
1s |
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corresponds to: |
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A) H2; |
B) He2; |
С) Н2−; |
D) Н2+. |
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14. The MO diagram (two nuclei of atoms lie on the z axis)
МО
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*(2pz)*(2px) *(2py)
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(2pz) |
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*(2s) |
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(2s) |
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corresponds to: |
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А) O2; |
B) N2; |
C) F2; |
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D) C2. |
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15. Linear combinations of which orbitals lead to the formation of the σ(s) and σ*(s) MOs?
1
2 3
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А) 1 and 2; B) 2 and 3; C) 2 and 5; D) 1 and 4.
16. The number of valence electrons in N2 and N22–, respectively is: А) 5 and 7; B) 10 and 8; C) 10 and 12; D) 3 and 5.
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17. The MO diagram (two nuclei of atoms lie on the z axis)
МО
E
*(2pz)*(2px)
*(2py)
(2px) (2py)
(2pz)
*(2s)
(2s)
corresponds to: |
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А) O2; |
B) N2; |
C) F2; |
D) Ne2. |
18. The number of valence electrons in F2 and F2−, respectively is: |
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А) 7 and 8; |
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B) 14 and 15; |
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C) 14 and 16; |
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D) 7 and 0. |
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19. The number of valence electrons in О2 and О2+, respectively is: |
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А) 12 and 13; |
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B) 2 and 3; |
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C) 6 and 7; |
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D) 12 and 11. |
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Using the MO theory, predict which a particle has the shortest bond |
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А) H2–; |
B) H2+; |
C) H2; |
D) Hе2+. |
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According to the MO theory, the bond order in CN− is: |
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А) 1; |
B) 1.5; |
C) 2; |
D) 3. |
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According to the MO theory, the bond order in the NO molecule is: |
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А) 1; |
B) 2.5; |
C) 2; |
D) 3. |
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3 . 4 . З а д а н и я д л я с а м о к о н т р о л я |
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Используя теорию МО, предскажите, какая частица диамагнитна: |
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A) O2+; |
Б) N2+; |
В) O2; |
Г) F2. |
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Согласно теории МО парамагнитной является молекула: |
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А) C2; |
Б) F2; |
В) N2; |
Г) O2. |
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Согласно теории МО парамагнитной является молекула: |
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А) H2; |
Б) F2; |
В) C2; |
Г) B2. |
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Используя теорию МО, предскажите, какая молекула является |
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наиболее прочной: |
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А) H2; |
Б) С2; |
В) В2; |
Г) Ne2. |
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5. |
Согласно теории МО в молекуле кислорода порядок связи равен: |
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A) 1; |
Б) 2; |
В) 1.5; |
Г) 2.5. |
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Согласно теории МО в молекуле Ne2 |
порядок связи равен: |
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A) 1; |
Б) 2; |
В) 0; |
Г) 3. |
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Согласно теории МО в молекуле углерода C2 порядок связи равен: |
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A) 1; |
Б) 2; |
В) 1.5; |
Г) 2.5. |
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Согласно теории МО в молекуле CO порядок связи равен: |
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А) 1; |
Б) 2; |
В) 3; |
Г) 4. |
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Согласно теории МО наименьший порядок связи в молекуле: |
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А) C2; |
Б) F2; |
В) N2; |
Г) O2. |
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10. Согласно теории МО наибольший порядок связи в частице: |
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А) H2+; |
Б) H2; |
В) He2; |
Г) He2+. |
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11. Согласно теории МО наибольший порядок связи в молекуле: |
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А) C2; |
Б) F2; |
В) N2; |
Г) O2. |
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12. Гетероядерная частица, изоэлектронная молекуле N2: |
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А) C2; |
Б) СО; |
В) NO−; |
Г) NO. |
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13. Энергетическая диаграмма МО
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АО МО АО |
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1s |
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cоответствует: |
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А) Н2; |
Б) Не2; |
В) Н2−; |
Г) Н2+. |
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МО
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(2px) |
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(2pz) |
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*(2s) |
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(2s) |
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cоответствует: |
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А) O2; |
Б) N2; |
В) F2; |
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Г) C2. |
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15. Линейная комбинация каких атомных орбиталей
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2 3
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приводит к образованию σ(s)- и σ*(s)-молекулярных орбиталей?
А) 1 и 2; Б) 2 и 3; В) 2 и 5; Г) 1 и 4.
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16. Число валентных электронов в частицах N2 и N22– соответственно:
А) 5 и 7; |
Б) 10 и 8; |
В) 10 и 12; |
Г) 3 и 5. |
17. Энергетическая диаграмма МО (за ось связывания двух ядер принята ось z)
МО
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*(2px) |
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*(2s) |
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соответствует частице: |
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А) O2; |
Б) N2; |
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В) F2; |
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Г) Ne2. |
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18. Число валентных электронов в частицах F2 |
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А) 7 и 8; |
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Б) 14 и 15; |
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В) 14 и 16; |
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Г) 7 и 0. |
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19. Число валентных электронов в частицах О2 |
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А) 12 и 13; |
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Б) 2 и 3; |
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В) 6 и 7; |
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Г) 12 и 11. |
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Используя теорию МО, предскажите, какая частица имеет |
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наименьшую длину связи: |
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А) H2–; |
Б) H2+; |
В) H2; |
Г) Hе2+. |
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Согласно теории МО порядок связи в ионе CN− равен: |
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А) 1; |
Б) 1.5; |
В) 2; |
Г) 3. |
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Согласно теории МО порядок связи в молекуле NO равен: |
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А) 1; |
Б) 2.5; |
В) 2; |
Г) 3. |
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4 . V A L E N C E B O N D T H E O R Y
4 . 1 . D i c t i o n a r y |
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English |
Russian |
Angular |
Угловая |
Bent |
Изогнутая |
Bond |
Связь |
Bond angle (valence angle) |
Угол связи (валентный угол) |
Bond distance or bond length |
Длина связи |
Вonding pair |
Связывающая пара |
Сentral atom |
Центральный атом |
Сoordination number |
Координационное число |
Dipole (electric) moment |
Дипольный (электрический) мо- |
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мент |
Disphenoidal |
Дисфеноидальная (искаженно- |
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тетраэдрическая) |
Ligand |
Лиганд |
Linear |
Линейная |
Lone pair |
Несвязывающая пара |
Molecule |
Молекула |
Molecular shape |
Молекулярная форма |
Multiple bond |
Кратная связь |
Non-polar bond |
Неполярная связь |
Octahedral |
Октаэдрическая |
Polar bond |
Полярная связь |
Polyatomic |
Многоатомный |
Single bond |
Одинарная связь |
Square planar |
Квадратная |
Square-based pyramidal |
Квадратная пирамидальная |
Tetrahedral |
Тетраэдрическая |
Trigonal bipyramidal |
Тригональная бипирамидальная |
Trigonal planar |
Треугольная |
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Trigonal pyramidal |
Тригональная пирамидальная |
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