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IP Secondary 3 Chemistry > Chapter 3 - Chemical Bonding > Flashcards

Chapter 3 - Chemical Bonding Flashcards

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1
Q

Ionic bonds

A

Electrostatic forces of attraction between oppositely charged ions

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2
Q

Structure of ionic compounds

A

Giant crystal lattice

  • formed from the 3-dimensional regular packing of positive and negative ions
  • bonded by strong electrostatic forces of attraction
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3
Q
  1. Ionic compounds have high melting and boiling points
A
  • A large amount of heat energy is required to overcome the strong forces of attraction between the oppositely-charged ions
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4
Q
  1. Ionic compounds are soluble in water but insoluble in organic solvents
A
  • Water molecules are polar molecules → form electrostatic forces with the ions, causing ions to separate and dissolving the compound
  • Organic solvents are non-polar molecules which cannot attract the ions and are hence unable to dissolve the compound.
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5
Q

Organic solvents (examples)

A
  • hexane
  • ethanol
  • turpentine
  • petrol
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6
Q
  1. Ionic compounds do not conduct electricity in solid but conduct electricity in molten or aqueous state
A
  • Solid state → ions are fixed within the crystal lattice and only vibrate about the lattice points
  • Molten/Aqueous state → ions are free to move (mobile) and can act as charge carriers to conduct electricity
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7
Q
  1. Ionic compounds are brittle and shatter when hit
A
  • When the lattice is hit, a layer of ions is shifted so that ions with the same charges are lined up together
  • These like charges repel each other and split the ionic lattice
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8
Q

Covalent bonds

A

Electrostatic forces of attraction between the positive nuclei of the 2 atoms and the bonding electrons shared between them

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9
Q

Chemical formula of methane

A

CH4

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10
Q

Chemical formula of hydrogen peroxide

A

H2O2

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11
Q

Structure of simple molecules (covalent)

A
  • Simple discrete molecules at lattice points
  • Atoms of the molecules are held by strong covalent bonds
  • Weak intermolecular forces (van der waals forces/hydrogen bonds) between the molecules
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12
Q

Hydrogen bonds

A
  • H directly bonded to N (nitrogen), O (oxygen) or F (fluorine)
  • Stronger than van der waals forces
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13
Q

Structure of macromolecules (covalent)

A
  • Atoms at lattice points that can be extended infinitely in 3 dimensions to form a giant lattice
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14
Q

Allotrope

A

Solid forms of an element with different molecular structures

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15
Q

Diamond (structure)

A
  • Each C atom forms 4 single covalent bonds with 4 other C atoms
  • Tetrahedral arrangement
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16
Q

Graphite (structure)

A
  • Each C atom forms 3 single covalent bonds with 3 other C atoms
  • The 4th unpaired valence electron of each C atom is delocalised along the layers
  • Layers are held by weak van der waals forces
  • Hexagonal arrangement (flat, parallel layers)
17
Q
  1. Simple molecules have low melting and boiling points
A
  • A small amount of heat energy is required to overcome the weak intermolecular forces of attraction between molecules
18
Q
  1. Simple molecules are generally soluble in organic solvents and insoluble in water
A
  • Exceptions: HCl (hydrogen chloride) exist as simple discrete molecules in organic solvents but ionises in water to form H+ and Cl-
19
Q
  1. Simple molecules do not conduct electricity in any state
A
  • There are no mobile charged particles (delocalised electrons/mobile ions) to carry charges
  • Exceptions: HCl (hydrogen chloride) ionises in water to form acidic solutions with mobile H+ and Cl- ions which conduct electricity
20
Q
  1. Simple molecules are generally soft
A
  • A small amount of energy is required to break and deform the weak intermolecular forces between molecules
21
Q
  1. Macromolecules have high melting and boiling points
A
  • A large amount of heat energy is required to overcome the strong covalent bonds between atoms in the molecules
22
Q
  1. Macromolecules are insoluble in all solvents
A
  • A large amount of energy is required to overcome the strong covalent bonds between atoms
23
Q
  1. Macromolecules do not conduct electricity in any state
A
  • Substances made up of neutral atoms and do not contain mobile charge particles (delocalised electrons/mobile ions) to carry charges
  • Exceptions: Graphite is a good conductor of electricity due to the presence of delocalised electrons along the layers to conduct electrcity
24
Q
  1. Macromolecules are generally hard
A
  • A large amount of energy is required to break and deform the strong covalent bonds between the atoms
  • Exceptions: Graphite is soft as layers are held by weak van der waals forces
25
Q

Metallic bonds

A

Strong electrostatic attraction between positive metal ions and negative delocalised ions (mobile valence electrons of the metal)

26
Q

Structure of metallic compounds

A

Giant metallic structure

  • a lattice of bonded positive metal ions
  • surrounded by a ‘sea of mobile electrons’
27
Q

What are factors affecting the strength of metallic bonds?

A
  1. Number of valence electrons

2. Size of metal ions

28
Q

1) Number of valence electrons

A
  • As the number of valence electrons increases, the charge of the positive metal ion increases
  • The number of delocalised electrons increases which then increases the strength of the metallic bond
29
Q

2) Size of metal ions

A
  • The smaller the metal ions, the closer the positive nuclei to the delocalised electrons
  • This results in a greater electrostatic attraction between the positive nuclei and the delocalised electrons → stronger metallic bonds
30
Q
  1. Metals have high melting and boiling points
A
  • A large amount of energy is required to overcome the strong electrostatic forces of attraction between positive metal ions and the negative delocalised electrons
31
Q
  1. Metals are generally insoluble in water and organic solvents
A
  • Exceptions: Reactive metals such as sodium and potassium can react with water to give hydrogen gas
32
Q
  1. Metals are good conductors of electricity
A
  • In the solid and molten states, delocalised electrons rapidly carry charges through the metal lattice
33
Q

Electrical conductivity increases with greater number of ________

A

valence electrons

34
Q
  1. Metals are good conductors of heat
A
  • When a metal is heated, delocalised electrons gain kinetic energy and moves faster to transfer the gained energy throughout the metal
  • Heat travels through the metal lattice as a result of rapid movement of delocalised electrons
35
Q

Define “malleable”

A

Can be hammered into different shapes without breaking

36
Q

Define “ductile”

A

Can be drawn into wires without breaking

37
Q
  1. Metals are malleable and ductile
A
  • Layers of atoms can slide over one another without breaking the strong metallic bonds

IP Secondary 3 Chemistry (9 decks)

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