Chemical Bonding Flashcards

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1
Q

What is chemical bond?

A

Force which holds atoms ions etc together

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2
Q

What is Electromagnet bond?

A

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

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3
Q

What is Electrovalence?

A

No. of unit charges on the ion

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4
Q

Octet rule

A

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

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5
Q

Lewis dot structure conditions

A

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

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6
Q

What is single bond?

A

2 atoms share 1 e’ pair

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7
Q

Formal charge formula

A

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

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8
Q

Limitations of octet rule

A
  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
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9
Q

Ionic/electrovalent bond depends on:

A

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

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10
Q

Ionization is endo or exo?

A

Endo

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11
Q

Electron affinity

A

-ve of energy change for e’ gain

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12
Q

Ionic bonds will form easily if

A

Ionization enthalpies are low and e’ gain enthalpy is high

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13
Q

Lattice enthalpy

A

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

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14
Q

Bond length

A

Dist btw nuclei of 2 bonded atoms

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15
Q

Bond angle

A

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

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16
Q

Bond enthalpy

A

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

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17
Q

Bond order

A

No of bonds btw 2 atoms in a molecule

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18
Q

Which 2 have identical bond orders?

A

Isoelectronic molecules and ions

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19
Q

Non polar covalent bond

A

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

20
Q

Polar covalent bond

A

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

21
Q

Dipole moment

A

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

22
Q

1 Debye(dipole)

A

3.33 × 10^-30C (coulomb) m

23
Q

Dipole moment for polyatomic molecules

A

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

24
Q

Why is dipole of BeF2 0?

A

2 equal bond dipoles in opp directions cancel each other

25
Q

Fajan’s rules

A
  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
26
Q

Postulates of VSEPR

A
  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
27
Q

Decreasing order of lone pair & bond pair

A

Lp-lp>lp-bp>bp-bp

28
Q

Arrangements of e’ pairs

A

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

29
Q

Bond enthalpy

A

Energy released when bond formed btw 2 H atoms

30
Q

Overlapping of atomic orbitals

A

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

31
Q

Strength of overlap

A

Greater overlap stronger bond

32
Q

What does VBT explain?

A

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

33
Q

Sigma bond

A

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

34
Q

Pi bond

A

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

35
Q

Stronger sigma or Pi?

A

Sigma

36
Q

Hybrid orbitals

A

Atomic orbitals that combine to form new set

37
Q

Hybridization

A

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

38
Q

Salient features of hybridization

A
  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
39
Q

Conditions for hybridization

A
  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
40
Q

Types of hybridization

A
  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°)
41
Q

Axial bonds

A

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

42
Q

Molecular orbital theory

A
  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
43
Q

Conditions for combining of atomic orbitals

A
  1. Same energy
  2. Same symmetry about the axis
  3. Must overlap to max extent
44
Q

Types of molecular orbitals

A

Sigma are symmetrical & Pi is asymmetrical

45
Q

Stability of molecules

A

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

46
Q

B.O =

A

½(Nb - Na)