Chemical Bonding

Question 1

What is chemical bond?

Answer 1

Force which holds atoms ions etc together

Question 2

What is Electromagnet bond?

Answer 2

Bond formed of electrostatic attraction btw +ve & -ve ions

Question 3

What is Electrovalence?

Answer 3

No. of unit charges on the ion

Question 4

Octet rule

Answer 4

Atoms combine either by transfer or sharing of valence e’s to have an octet

Question 5

Lewis dot structure conditions

Answer 5

Bond is formed due to sharing
Each atom contributes at least 1 e
Atoms attain noble gas configuration due to sharing

Question 6

What is single bond?

Answer 6

2 atoms share 1 e’ pair

Question 7

Formal charge formula

Answer 7

F C = Valence e’s(total) - no of lone pairs(total) - ½[no of bonding e’s(total)]

Question 8

Limitations of octet rule

Answer 8

1. Not universal
2. In some compounds, there are < 8 valence e’s
3. In molecules with odd no of e’s, rule is not satisfied
4. Some have > 8 valence e’s(expanded octet)
5. Some noble gases also combine to form compounds
6. Does not account on shape of molecules
7. Doesn’t explain relative stability of molecules and their energy

Question 9

Ionic/electrovalent bond depends on:

Answer 9

Formation of +ve/-ve ions
Arrangement of them
Formation includes ionization(removal of e’) & addition of e’

Question 10

Ionization is endo or exo?

Answer 10

Endo

Question 11

Electron affinity

Answer 11

-ve of energy change for e’ gain

Question 12

Ionic bonds will form easily if

Answer 12

Ionization enthalpies are low and e’ gain enthalpy is high

Question 13

Lattice enthalpy

Answer 13

Energy required to completely separate 1 mole of a solid ionic compound to gaseous ions

Question 14

Bond length

Answer 14

Dist btw nuclei of 2 bonded atoms

Question 15

Bond angle

Answer 15

Angle btw orbitals having bonding e’ pairs around the central atom

Question 16

Bond enthalpy

Answer 16

Energy required to break 1 mole of bonds of a type btw 2 atoms on a gaseous state
Unit is KJmol^-1

Question 17

Bond order

Answer 17

No of bonds btw 2 atoms in a molecule

Question 18

Which 2 have identical bond orders?

Answer 18

Isoelectronic molecules and ions

Question 19

Non polar covalent bond

Answer 19

Bond formed as a result of E’ btw 2 identical nuclei

Question 20

Polar covalent bond

Answer 20

E’ pair btw 2 atoms gets displaced towards more e’ -ve atom

Question 21

Dipole moment

Answer 21

Product of magnitude of charge & dist btw centers of +ve & -ve charge

Question 22

1 Debye(dipole)

Answer 22

3.33 × 10^-30C (coulomb) m

Question 23

Dipole moment for polyatomic molecules

Answer 23

Independent of individual dipole moment of bonds and spatial arrangement of bonds

Question 24

Why is dipole of BeF2 0?

Answer 24

2 equal bond dipoles in opp directions cancel each other

Question 25

Fajan's rules

Answer 25

1. Small the cation, larger the anion, greater the covalent character 2. Greater charge of cation, more covalent char 3. Cation polarises anion, pull e' charge toward itself increasing electronic charge btw the 2 4. Polarizing power of cation, polarisability of anion & extent of polarization of anion are the factors

Question 26

Postulates of VSEPR

Answer 26

1. Shape of molecule depends on no of valence shell e' pairs 2. Pairs of e's on valance shell repel since e' cloud are -vely charged 3. Pair of e's occupy positions that minimize repulsion & and maximize distance 4. Valence shell is taken as a sphere with e' pairs on the spherical surface at max dist from 1 another 5. Multiple bond is treated as single e' pair & 2 or 3 e' pairs as single super pair 6. Applicable to 2 or more resonance structures as well

Question 27

Decreasing order of lone pair & bond pair

Answer 27

Lp-lp>lp-bp>bp-bp

Question 28

Arrangements of e' pairs

Answer 28

Linear, trigonal planar, tetrahedral, trigonal-bipiramidal, octahedral

Question 29

Bond enthalpy

Answer 29

Energy released when bond formed btw 2 H atoms

Question 30

Overlapping of atomic orbitals

Answer 30

Minimum energy state when 2 H atoms are near & their orbitals go penetration

Question 31

Strength of overlap

Answer 31

Greater overlap stronger bond

Question 32

What does VBT explain?

Answer 32

Shape, formation & directional properties in polyatomic molecules and overlap & hybridization of atomic orbitals

Question 33

Sigma bond

Answer 33

End to end overlap along internuclear axis(head on or axial)

Question 34

Pi bond

Answer 34

Atomic orbitals axes remain parallel to each other & perpendicular to internuclear axis

Question 35

Stronger sigma or Pi?

Answer 35

Sigma

Question 36

Hybrid orbitals

Answer 36

Atomic orbitals that combine to form new set

Question 37

Hybridization

Answer 37

Intermixing of orbitals of diff energies to redistribute their energies forming new set with equivalent energies

Question 38

Salient features of hybridization

Answer 38

1. No of hybrid orbitals = no of atomic orbitals that get hybridized 2. Always equivalent in energy and shape 3. Form stable bonds 4. Have min repulsion btw e' pairs & a stable arrangement

Question 39

Conditions for hybridization

Answer 39

1. Orbitals jn valencebshell are hybridized 2. They should have almost equal energy 3. Promotion of e' is not necessary 4. Even filled orbitals can participate

Question 40

Types of hybridization

Answer 40

1. Sp: 1s 1p- 2 sp orbitals 50% s & p char(diagonal) 2. Sp²: 1s 2p- 3 sp² orbitals(trigonal planar)(180°) 3. Sp³: 1s 3p- 4 sp³ orbitals, 25% s 75% p char(tetrahedron)(109.5°)

Question 41

Axial bonds

Answer 41

bonds- 1 lying above the other lying below the equatorial plane(90°)

Question 42

Molecular orbital theory

Answer 42

1. E's are present in various molecular orbitals like that of atoms in atomic orbitals 2. Atomic orbitals of comparable energies & proper symmetry combine to form molecular orbitals 3. E' is influenced by 2 or more nuclei 4. No of molecular orbitals formed = no of combing atomic orbitals(BMO & ABMO) 5. Bmo has greater stability & lower energy than abmo 6. E' distribution around nuclei is given by molecular orbital 7. Molecular orbitals are filled based on aufbau, Pauli's principle and Hund's rule

Question 43

Conditions for combining of atomic orbitals

Answer 43

1. Same energy 2. Same symmetry about the axis 3. Must overlap to max extent

Question 44

Types of molecular orbitals

Answer 44

Sigma are symmetrical & Pi is asymmetrical

Question 45

Stability of molecules

Answer 45

Molecule is stable if: Nb > Na, Nb is no of e's of BMO & Na of ABMO

Question 46

B.O =

Answer 46

½(Nb - Na)