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Chemistry 3AB FO REAL > Chapter 3 Chemical Bonding > Flashcards

Chapter 3 Chemical Bonding Flashcards

1
Q

What are Metallic elements characterized by?

A

Low ionization energy

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2
Q

What are features of a low ionization energy?

A

•Allows metallic elements to achieve a noble gas electron configuration by releasing their

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3
Q

What are the Physical Properties of a substance?

A
  • MP
  • Malleability
  • Ability to conduct heat/electricity

-> Patterns in these properties suggest 4 distinct classes of substance.

  1. Metallic
  2. Ionic
  3. Covalent molecular
  4. Covalent network
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4
Q

What are metallic elements characterised by?

A

Low Ionisation Energy

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5
Q

What does a low ionisation energy allow Metals to do?

A

It allows metallic elements to achieve a noble gas electron configuration by releasing their valence electrons to form positive metal ions and free electrons.

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6
Q

Describe the bonding within a Metallic lattice.

A

Bonding within the metallic lattice is due to strong electrostatic attraction between stationary metal ions (+charge) and mobile, delocalised valence electrons (-charge) that form the sea of electrons.

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7
Q

Why is the metallic bonding a non-directional bond?

A

Because it occurs equally in all directions between all metal ions and the surrounding sea of electrons.

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8
Q

What properties do Metals have?

A
  1. Good Conductors of Electricity.
  2. Good Conductions of Heat.
  3. Malleable and Ductile.
  4. High Melting and Boiling Points.
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9
Q

Explain why Metals are Good Conductors of Electricity?

A
  • Valence electrons that form the sea of electrons are mobile (can move freely).
  • When a voltage is applied to a metal, electrons in the mobile sea of electrons move towards the positive terminal of the power supply.
  • The positive metal ions remain stationary as they are in fixed positions.
  • The ability of the mobile sea of electrons to conduct charge explains why metals are good conductors of electricity.
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10
Q

Explain why Metals are Good Conductors of Heat.

A
  • Electrons within the sea of electrons are mobile and so can carry heat energy (as kinetic energy) through the metal lattice.
  • The vibration of metallic ions also contributes to the flow of heat through the metal lattice.
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11
Q

Explain why Metals are Malleable and Ductile?

A
  • Bonding between metal ions and the sea of electrons is non-directional.
  • Consequently layers of metal atoms can move in relation to each other without breaking the bonds, between metal ions and the sea of electrons, that hold the structure together.
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12
Q

Explain why Metals have High Melting and Boiling Points?

A
  • Strong attractive forces between the metal ions and sea of electrons hold the metallic lattice together.
  • As a consequence a high temperature is needed to disrupt the lattice and allow the metal to melt.
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13
Q

What are Ionic Compounds?

A

They are form by a combination of metallic elements (NH4+ ions) with non-metallic elements, eg. NaCl, CaO, MgSO4, Al(NO3)3, NH4Cl and so on.

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14
Q

How does bonding occur in the Ionic lattice?

A

It is due to the strong electrostatic attraction between neighbouring positive and negative ions.

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15
Q

Does the repulsive forces between like charged particles occur?

A

Yes but these forces are much weaker than the attractive forces of unlike charges.

-This happens as like charges are on average further apart than unlike charges and electrostatic forces reduce considerably as the distance between the charged particles increases.

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16
Q

List all the properties of Ionic Compounds.

A
  1. Poor conductors of electricity in the solid phase.
  2. Good conductors of electricity when molten.
  3. Good conductors of electricity when in aqueous solution.
  4. Hard and brittle.
  5. High melting and boiling points.
17
Q

Explain why Ionic Compounds are Poor Conductors of electricity in the solid phase?

A
  • For a substance to conduct electricity, the charged particles within it must be free to move independently of one another.
  • As the ions are tightly held in fixed positions within the ionic lattice they are unable to move and carry charge.
  • Electrons within the ionic lattice are unable to carry charge through the ionic lattice as they are strongly attached to the individual ions.
  • An absence of mobile charged particles means ionic solids are non-conductors of electricity.
18
Q

Explain why Ionic Compounds are Good Conductors of electricity when molten?

A
  • In the molten phase, ions are mobile and free to move and carry charge through the ionic liquid.
  • Both positive and negative ions carry charge.
  • Positive ions move towards the negative electrode while negative ions move towards the positive electrode.
19
Q

Explain why Ionic Compounds are Good Conductors of electricity when in aqueous solution?

A
  • In an aqueous solution individual ions from the ionic solid are mobile and free to move independently of one another.
  • Their mobility and charge enable them to conduct an electric current through the ionic solution.
  • Both positive and negative ions are involved in conducting the current.
  • The current consists of positive ions moving toward the negative electrode and negative ions moving towards the positive electrode.
20
Q

Explain why Ionic Compounds have High melting and Boiling points.

A
  • Ionic bonds are strong electrostatic attractive forces between ions.
  • These strong attractive forces extend throughout the ionic lattice keeping individual ions in fixed positions.
  • Thus a high temperature (high energy) is needed to disrupt (melt) the ionic lattice.
21
Q

What is a Covalent bond?

A
  • A covalent bond occurs whenever non-metal elements bond to other non-metal elements.
  • In a covalent bond, valence electrons are shared between the bonded atoms so that each atom achieves a noble gas configuration.
  • Covalent bonds are directional, unlike metallic bonds.
22
Q

What two type of substances do Covalent bonds occur in?

A
  1. Covalent Molecular - mostly non-metal elements

2. Covalent Network (eg. Boron, Carbon (graphite/diamond), Silicon, Silicon Dioxide,etc)

23
Q

How are Covalent molecular substances bonded?

A

Atoms are bonded by covalent bonds to form strongly bonded clusters of atoms, known as molecules.

24
Q

List all the properties of Covalent Molecular substance.

A
  1. Non-conductors of electricity in either solid, liquid or aqueous phase.
  2. Soft and weak.
  3. Low to moderate MP and BP.
25
Q

Explain why Covalent Molecular substances are non-conductors of electricity in either solid, liquid or aqueous phase?

A
  • Electrons in these substances are localised within each atom’s electron cloud or as shared electrons within covalent bonds.
  • None of these electrons are free to move independently.
  • Consequently the absence of any mobile charged particles means these substances are non-conductors of electricity.
26
Q

Explain why Covalent Molecular substances are Soft and Weak?

A
  • Strong covalent bonds form only between atoms within molecules.
  • Forces between molecules are limited to a variety of weak attractions known as van der Waals forces.
  • Consequently the molecules are easily separated from each other.
  • Hence these substances are weak and soft.
27
Q

Explain why Covalent Molecular substances are Low to moderate melting and boiling points.

A
  • When a molecular substance melts or boils, only intermolecular forces (the forces between molecules) are broken or overcome.
  • Intermolecular forces are limited to a variety of week attractions known as van der Waals forces.
  • Thus the weakly bonded lattice of molecules in the solid phases is easily disrupted by heat energy to form a liquid or gas.
  • It must be understood that the strong covalent bonds occurring between atoms that form the molecule are unaffected when a substance melts or boils.
28
Q

How are Covalent Network substances bonded?

A
  • They are bonded to one another by covalent bonds, however, molecules do not exist in these structures.
  • Instead atoms form covalent bonds with all neighbouring atoms resulting in a continuous array of covalently bonded atoms.
29
Q

List all the properties of a Covalent Network substance.

A
  1. Non-conductors of heat/electricity.
  2. Very hard and brittle.
  3. Very high melting and boiling points.
30
Q

Explain why Covalent Network substances are Non-conductors of heat or electricity.

A
  • Electrons in these substances are held in fixed positions within the atom’s shells, lone pairs or covalent bonds.
  • As the electrons are not free to move independently they are unable to conduct electricity or heat through the substance.
  • Graphite, an allotrope of carbon is a notable exception where some valence electrons are delocalised and so are free to move throughout the structure.
  • Consequently Graphite is a good conductor of electricity.
31
Q

Explain why Covalent Network substances are Very Hard and Brittle?

A
  • Strong covalent bonds occur between all atoms within a covalent network structure.
  • This continuous array of strongly bonded atoms is difficult to disrupt and so these substances are characteristically hard and brittle.
  • Graphite is a notable exception where its atoms are covalently bonded into rings of 6 carbon atoms.
  • These rings interlock to form strongly bonded, flat, two dimensional layers.
  • As only weak bonding forces occur between these layers they are able to slip over one another with ease.
  • This causes graphite to be a soft material.
32
Q

Explain why Covalent Network substances have Very High MP and BPs.

A
  • Strong covalent bonds occur between all atoms within the structure.
  • A very high temperature (high energy) is needed to disrupt this continuous array of strongly bonded atoms.

Chemistry 3AB FO REAL (11 decks)

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