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Chemical Bonding Flashcards

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1
Q

What is a chemical bond?

A

Chemical bond is the force which holds two or more atoms together in a stable molecule

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2
Q

What is an atom?

A

An atom is the smallest unit of matter taking part in a chemical reaction

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3
Q

What is an atom built up of?

A

Sub-atomic particles - protons, neutrons, electrons

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4
Q

What combines to forma molecule?

A

Two or more atoms (metallic or non-metallic)

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5
Q

What are elements?

A

They are pure substances made up of one kind of atoms having the same atomic number

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6
Q

Name the type of atoms involved in chemical combination

A
  1. Metallic Elements

2. Non-metallic elements

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7
Q

Give the no. of valence electrons in the valence shell of a metallic atom

A

They have 1, 2, 3 electrons in the valence shell

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8
Q

What is the nature of metallic ions?

A

Metallic ions become positively charged ions (cations) because they lose 1, 2, or 3 electrons to attain stable electronic configuration

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9
Q

Give the no. of valence electrons in the valence shell of a non-metallic atom

A

They have 4, 5, 6, or 7 electrons in their valence shell

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10
Q

What is the nature of non-metallic ions?

A

They gain (4), 3, 2, or 1 electrons and become negatively charged ions (anions)

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11
Q

Name the two means by which atoms combine to form a molecule

A
  1. Transfer of valence electrons from a metallic atom to a non-metallic atom
  2. Sharing of valence electrons between two atoms (generally both non-metallic)
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12
Q

Give the mass of a proton

A

1 a.m.u [C-12 standard]

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13
Q

Give the mass of an electron

A

negligible

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14
Q

Give the mass of a neutron

A

1 a.m.u [C-12 standard]

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15
Q

Why are noble gases inert or unreactive?

A

They have stable electronic configuration i.e. their valence shell is complete. They have 2 electrons in the outermost shell [He] or 8 electrons in the outermost shell. Therefore, they do not lose, gain or share electrons.

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16
Q

Why are atoms of other elements other than noble gases chemically reactive?

A

They have unstable electronic configuration. They can lose, gain or share electrons because their outermost shell is incomplete.

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17
Q

What is the reason for chemical bonding between atoms?

A

The driving force for atoms to combine is the tendency of each atom to attain a stable electronic configuration of the nearest noble gas

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18
Q

What is duplet rule?

A

Two electrons in the valence shell

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19
Q

What is octet rule?

A

8 electrons in the valence shell

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20
Q

Name the periodic properties that affect bond formation of an ionic or covalent compound

A
  1. Ionisation Potential
  2. Electronaffinity
  3. Electronegativity
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21
Q

How does IP affect the formation of an ionic bond?

A

Lower the value of IP of a metallic atom, greater the ease of formation of the cation

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22
Q

How does electronaffinity affect the formation of an ionic bond?

A

Higher the value of E.A. of a non-metallic atom, grater the ease of formation of the anion

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23
Q

How does E.N. affect the formation of an ionic bond?

A

Larger the E.N. difference between combining atoms, electron transfer takes place easily

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24
Q

Name the factors which affect the formation of a covalent bond

A
  1. I.P. should be high between both atoms/elements
  2. E.A. should be high between both atoms/elements
  3. E.N. should be high between both atoms/elements
  4. E.N.D should be negligible between the two combining atoms
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25
Q

How does formation of electrovalent compounds take place?

A

It involves transfer of valence electrons from one atom generally metallic to another atom - generally non-metallic

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26
Q

Give the equation for a metallic atom losing electrons in ionic bonding

A

X [elec. config. 2,8,1]

X - 1e- –> X 1+ Cation (positive ion 2,8)

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27
Q

Give the equation for a non-metallic atom gaining electrons in ionic bonding

A

Y [elec. config. 2,8,7]

Y + 1e- –> Y 1- Anion (negative ion 2,8,8]

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28
Q

What are cations and anions?

A

They are oppositely charged particles, which attract one another to form an electrovalent bond leading to the formation of an electrovalent compound.

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29
Q

What is electrovalent bond formation due to?

A

Electrostatic force of attraction between two oppositely charged ions

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30
Q

Define ionic bond

A

The chemical bond formed between two atoms by transfer of one or more electrons from the atom of a metallic - electropositive element to an atom of a non-metallic - electronegative element

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31
Q

Define ionic compound

A

The chemical compound formed as a result of transfer of one or more electrons from the - atom of a metallic -electropositive element to an - atom of a non-metallic - electronegative element

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32
Q

Define electrovalency

A

The number of atoms donated or accepted by the valence shell of an atom of an element - so as to achieve stable electronic configuration

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33
Q

Differentiate between atoms X and Y vs ions X and Y on the basis of nature

A

Atoms X and Y - electrically neutral particles, whereas ions X 1+ and Y 1- are electrically charged particles (cations, anions)

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34
Q

Differentiate between atoms X and Y vs ions X and Y on the basis of existence

A

Atoms X and Y may or may not exist independently, whereas ions X 1+ and Y 1- exist independently in solution

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35
Q

Differentiate between atoms X and Y vs ions X and Y on the basis of valence shell

A

In atoms X and Y, outermost shell may or may not have duplet or octet, whereas ions X 1+ and Y 1- have complete duplet and octet

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36
Q

What happens to an atom or ion during oxidation?

A

It loses electrons

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37
Q

What happens to an atom or ion during reduction?

A

It gains electrons

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38
Q

Give an alternative form of the equation X - 1e- –> X 1+

A

X –> X 1+ + 1e-

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39
Q

How is a sodium compound formed?

A

As a result of transfer of one valence electron from metallic sodium atom [At. No. 11 - 2,8,1] to a non-metallic chlorine atom [At. No. 17 - 2,8,7]

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40
Q

How does sodium attain s.e.c in the formation of sodium chloride?

A

Sodium atom attains s.e.c of the nearest noble gas - Neon by losing one electron from its valence shell and becomes a positively charged sodium ion (cation) - Na 1+

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41
Q

How does chlorine attain s.e.c in the formation of sodium chloride?

A

Chlorine atom attains s.e.c of the nearest noble gas - Argon by gaining one electron in its valence shell and becomes a negatively charged chlorine ion (anion) - Cl 1-

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42
Q

Give examples of the ionic bonds sodium and chloride from with other elements

A
  1. K [At. No. 19] and Cl [At. No. 17] form KCl - Potassium chloride
  2. Na [At. No. 11] and S [At. No. 16] form Sodium sulfide - Na2S
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43
Q

Give the ionic equation for the formation of sodium chloride

A

Na - 1e- –> Na 1+ [oxidation]
Cl + 1e- –> Cl 1- [reduction]
Na + Cl –> Na 1+ Cl 1- –> NaCl

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44
Q

How is calcium oxide formed?

A

It is formed as a result of transfer of two valence electrons from metallic calcium atom [At. No. 20 - 2,8,8,2] to non-metallic oxygen atom [At. No. 8 - 2,6]

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45
Q

How does calcium attain s.e.c in the formation of calcium oxide?

A

Calcium atom attains s.e.c of the nearest noble gas - Argon by losing two electrons from its valence shell and becomes a positively charged calcium ion (cation) - Ca 2+

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46
Q

How does oxygen atom attain s.e.c in the formation of calcium oxide?

A

Oxygen attains s.e.c of the nearest noble gas Neon by gaining two electrons in its valence shell and becomes a negatively charged oxide ion (anion) - O 2-

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47
Q

Give the ionic equation of the formation of CaO

A

Ca - 2e- –> Ca 2+ [oxidation]
O + 2e- –> O 2- [reduction]
Ca + O –> Ca 2+ + O 2- –> CaO

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48
Q

How is magnesium chloride formed?

A

It is formed as a result of transfer of two valence electrons from one metallic magnesium atom [At. No. 12 - 2,8,2] to two non-metallic chlorine atoms [At. No. 17 - 2,8,7]

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49
Q

How does magnesium atom attain s.e.c in the formation of magnesium chloride?

A

Magnesium atom attains s.e.c of the nearest noble gas Neon by losing two electrons from its valence shell and becomes a positively charged magnesium ion (cation) - Mg 2+

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50
Q

How does chlorine atom attain s.e.c in the formation of magnesium chloride?

A

Chlorine atom attains stable electronic configuration of the nearest noble gas argon by gaining one electron in its valence shell and becomes a negatively charged chloride ion [anion] - Cl-

51
Q

How does the transfer of electrons take place in the formation of magnesium chloride?

A

Magnesium atom donates two electrons [is oxidised], whereas chlorine atom accepts only one electron [is reduced] to give chlorine ion. Thus, to accept another magnesium atom, there must be another chlorine atom

52
Q

Give the ionic equation of the formation of MgCl2

A

Mg - 2e- –> Mg 2+ [oxidation]
2Cl + 2e- –> 2Cl- [reduction]
Mg + 2Cl –> Mg 2+ 2Cl 1- –> MgCl2

53
Q

Define the formation of covalent compounds

A

It involves sharing of electron pairs between one atom - generally non-metallic and another atom - also non-metallic. Electrons in the valence shell are mutually shared by the atom of each element such that each atom acquires a stable electronic configuration

54
Q

Which atoms share 1 pair of electrons?

A

Non-metallic atoms having 7 [or 1] valence electrons

55
Q

Which atoms share 2 pair of electrons?

A

Non-metallic atoms having 6 valence electrons

56
Q

Which atoms share 3 pair of electrons?

A

Non-metallic atoms having 5 valence electrons

57
Q

How do dissimilar non-metallic atoms form covalent molecules?

A

By sharing electron pairs

58
Q

Define covalent bond

A

The chemical bond formed due to mutual sharing of electrons between the given pairs of atoms of non-metallic elements. Bond formed by a shared pair of electrons, each bonding atom contributing one electron to the pair

59
Q

On what does the bond being single, double or triple covalent depend>

A

On the no. of electron pairs shared

60
Q

Define covalent compound

A

It is the chemical compound formed due to mutual sharing of electrons between the given pairs of atoms thereby forming a covalent bond between them

61
Q

Define covalency

A

The no. of electron pairs which an atom shares with one or more atoms of the same or different kind to achieve stable electronic configuration

62
Q

When are covalent compounds said to be non-polar?

A

When shared pair of electrons are equally distributed between the two atoms

63
Q

When are covalent compounds said to be polar?

A

When shared pair of electrons unequally distributed between the two atoms

64
Q

Comment on the nature of the non-polar covalent molecule

A

No charge separation takes place. The covalent molecule is symmetrical and electrically neutral.

65
Q

Comment on the nature of the polar covalent molecule

A

Charge separation takes place. The atom which attracts electrons more strongly develops a slight negative charge.

66
Q

Give examples of non-polar covalent compounds

A

H2, Cl2, O2, N2, CH4, CCl4

Hydrogen, Chlorine, Oxygen, Nitrogen, Methane, Carbon tetrachloride

67
Q

Give examples of polar covalent compounds

A

H2O, NH3, HCl

Water, Ammonia, Hydrochloric acid

68
Q

How is a hydrogen molecule formed?

A

Each of the two ‘H’ atoms contributes one electron so as to have one shared pair of electrons between them. Both atoms attain stable - duplet structure, resulting in the formation of a single covalent bond [H-H] between them.

69
Q

How is a chlorine molecule formed?

A

Each of the two ‘Cl’ atoms contributes one electron so as to have one shared pair of electrons between them. Both atoms attain stable octet structure, resulting in the formation of a single covalent bond [Cl-Cl] between them.

70
Q

What is the nearest noble gas for oxygen?

A

Neon [2,8]

71
Q

What is the nearest noble gas for hydrogen?

A

Helium [2]

72
Q

What is the nearest noble gas for chlorine?

A

Argon [2,8,8]

73
Q

How is an oxygen molecule formed?

A

Each of the two ‘O’ atoms contributes two electrons so as to have two shared pairs of electrons between them. Both atoms attain stable octet structure, resulting in the formation of a double covalent bond [O=O] between them.

74
Q

How is a nitrogen molecule formed?

A

Each of the two ‘N’ atoms contributes three electrons so as to have three shared pairs of electrons between them. Both atoms attain stable octet structure, resulting in the formation of a triple covalent bond [N=N] between them.

75
Q

How many electrons does carbon need to attain stable octet?

A

4 electron

76
Q

Which is the nearest noble gas for carbon?

A

Neon [2,8]

77
Q

Which is the nearest noble gas for chlorine?

A

Argon [2,8,8]

78
Q

How many electrons does chlorine need to achieve stable octet?

A

One electron

79
Q

How is carbon tetrachloride formed?

A

One atom of carbon shares four electron pairs - one with each of the four atoms of chlorine - four single covalent bonds

80
Q

How does the formation of methane take place?

A

One atom of carbon shares four electron pairs - one with each of the four atoms of hydrogen - four single covalent bonds

81
Q

How does the formation of water take place?

A

Each of the two hydrogen atoms shares an electron pair with the oxygen atom such that hydrogen acquires a duplet configuration and oxygen an octet configuration - resulting in the formation of - two single covalent bonds [H-O-H] in the molecule of water

82
Q

How does the formation of ammonia take place?

A

One atom of nitrogen shares three electron pairs with each of the three atoms of hydrogen

83
Q

What are lone pairs of electrons?

A

They are a pair of electrons that are not shared with any atom

84
Q

Name a stable positive ion

A

Hydronium ion

85
Q

Addition of acid to water results in release of which ion from the acid?

A

H+ ion

86
Q

What is a coordinate bond?

A

Type of covalency which involves one of the combining atoms contributing both of the shared electrons i.e. a bond formed by a shared pair of electrons with both electrons coming from the same atom

87
Q

Give another name for covalent bond

A

Dative or co-ionic bond

88
Q

Name compounds containing electrovalent and covalent bond

A

NaOH, CaCO3

89
Q

Name compounds containing coordinate and covalent bond

A

CO, HNO3

90
Q

Name compounds containing electrovalent, covalent and coordinate bond

A

NH4Cl, K4 [Fe(CN)6] - Ferricyanide

91
Q

What is form of the existence of ionic compounds?

A

Crystalline hard solids (at room temp.)

92
Q

What is form of the existence of covalent compounds?

A

Gases, liquids or soft solids

93
Q

Name the constituent units for ionic compounds

A

Ions (metallic, non-metallic)

94
Q

Name the constituent units for covalent compounds

A

Molecules

95
Q

How is the force of attraction in ionic compounds?

A

Strong

96
Q

Where do electrostatic forces exist in ionic compounds?

A

Between ions

97
Q

Why are ionic compounds hard solids?

A

Ions are closely packed with strong force of attraction, hence ionic compounds are hard solids

98
Q

What is the volatility of ionic compounds?

A

Non-volatile

99
Q

What is the mp and bp of ionic compounds?

A

They have a high melting and a high boiling point

100
Q

Why do ionic compounds have high melting and boiling points?

A

Strong electrostatic force of attraction between ions. Large amount of energy required to break the force of attraction

101
Q

Ionic compounds - conductors of heat

A

Good conductors of heat

102
Q

In which state are ionic compounds good conductors of electricity?

A

Molten or aq. soln. state

103
Q

Why are ionic compounds (soln.) good conductors of electricity?

A

Strong electrostatic force keeps ions in fixed position in the solid state. The force is weakened in the molten state and disappears in soln. state, hence free ions formed migrate to oppositely charged electrodes

104
Q

Why are ionic compounds soluble in water but not in organic solvents?

A

Water (polar solvent) has a high dielectric constant, thus resulting in free ions. Organic solvents (non-polar) have low dielectric constants and do not cause dissolution

105
Q

What is dielectric constant?

A

Capacity to weaken the force of attraction

106
Q

What kind of reactions do ionic compounds undergo?

A

High speed ionic reactions

107
Q

Why do ionic compounds undergo high speed ionic reactions?

A

Free ions formed in solution, rapidly regroup in solution

108
Q

What happens to ionic compounds on passage of electric current?

A

Undergo electrolytic dissociation

109
Q

What does the process of electrolytic dissociation involve for ionic compounds?

A

Separation of ions already present in the ionic compound

110
Q

How is the force of attraction in covalent compounds?

A

Weak

111
Q

Which forces exist between molecules in covalent compounds?

A

Vander Waal’s forces

112
Q

Why are covalent compounds gaseous or liquid or soft solids?

A

Molecules have weak forces of attraction bet. them

113
Q

What is the volatility of covalent compounds?

A

Volatile

114
Q

What is the mp and bp of covalent compounds?

A

Low mp and low bp

115
Q

Why do covalent compounds have low melting and boiling points?

A

Weak Vander Waals forces of attraction between molecules. Less amount of energy required to break this force of attraction

116
Q

Covalent compounds - conductors of heat

A

Bad or non-conductors of heat

117
Q

Why are covalent conductors non-conductors of heat in any state?

A

Non-polar covalent compounds contain molecules and not free ions, hence are non-conductors. Polar covalent compounds show charge separation and dissociate in H2O

118
Q

In which state can covalent compounds undergo electrolysis?

A

In soln. state

119
Q

Why are covalent compounds not soluble in organic solvents and not in water?

A

Organic solvents (non polar) dissolve non-polar covalent compounds (like dissolves like). Water cannot dissolve non-polar covalent compounds , but dissolves polar

120
Q

What kind of reactions do covalent compounds undergo?

A

Slow speed molecular reactions

121
Q

Why do covalent compounds undergo slow speed molecular reactions?

A

Covalent molecules are first broken and new bonds are slowly established

122
Q

In which state do covalent compounds undergo ionisation?

A

In soln. state, on passage of electric current

123
Q

What does ionisation of covalent compounds involve?

A

Formation of ions from molecules from molecules which are not in ionic state

Chemistry (4 decks)

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