chapter 5 chemical bonds
TRANSCRIPT
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Chapter 5
Chemical Bonds
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Formation of Chemical Bonds
• Types of chemical bonds:
1. Ionic bond: formed when atom joined together by transferring of electrons between metal and non-metal atom
2. Covalent bond: formed when atom joined together by sharing electron between non-metal and non-metal atom
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Ionic Bonds
• Formed when atom joined together by transferring of electrons between metal and non-metal atom
Metal atom Non-metal atom e
donate electron receive electron
Achieve the stable electron arrangement
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Formation of ions
Neutral atom
Cation (+)
Anion (-)
Donate electrons Accepts electrons
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Aluminium, Al
2.8.3
Al
Donate 3 electrons
Al
3+
2.8
Aluminium atom, Al Aluminium ion, Al 3+
Al → Al + 3e 3+ -
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Oxygen, O
2.6
O
Accepts 2 electrons
O
2-
2.8
Oxygen atom, O Oxide ion, O 2-
O + 2e → O 2- -
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Formation of ionic bonds
• Ionic compounds
Compounds that are formed through ionic bonds
Lets investigate the formation of
sodium chloride, NaCl
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2.8.1
Na Cl +
2.8.7
2.8 2.8.8
Cl
-
Na
+
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Explain the formation of sodium chloride
+
-
- +
+
-
1. Sodium atom, Na with the electron arrangement 2.8.1
2. Chlorine atom, Cl with the electron arrangement 2.8.7
3. Sodium atom, Na will donate 1 electron to achieve the stable electron arrangement to form sodium ion, Na
Na → Na + e
4. Chlorine atom, Cl will receive 1 electron to achieve the stable electron arrangement to form chloride ion, Cl
Cl + e → Cl
5. One sodium ion, Na and one chloride ion, Cl attracted by strong electrostatic force to form sodium chloride, NaCl
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F + e → F
5. One magnesium ion, Mg and two fluoride ion, F attracted by strong electrostatic force to form magnesium fluoride, MgF
4. Fluorine atom, F will receive 1 electron to achieve the stable electron arrangement to form fluoride ion, F
Mg → Mg + 2e
3. Magnesium atom, Mg will donate 2 electron to achieve the stable electron arrangement to form magnesium ion, Mg
Explain the formation of magnesium fluoride
2+
-
- 2+
2+
-
1. Magnesium atom, Mg with the electron arrangement 2.8.2
2. Fluorine atom, F with the electron arrangement 2.7
2
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2.8.2
Mg
F
+
2.7
2.7
F
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2.8 2.8
F
-
Mg
2+
2.8
F
-
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Exercise
• Explain the formation of ionic bond of:
1. Lithium fluoride
2. Sodium oxide
3. Magnesium oxide
4. Boron oxide
5. Aluminium oxide
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Covalent Bonds
• Formed when atom joined together by sharing electron between non-metal and non-metal atom
• Types of covalent bonds:
1. single covalent bonds
2. double covalent bonds
3. triple covalent bonds
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Single covalent bonds
• A covalent bond formed when a pair of electrons is shared between two atoms
Lets investigate the formation of hydrogen molecule
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H
1
H +
1
H H
2 2
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5. A single covalent compound with formula H is formed
4. Two hydrogen atom share pairs of electron to achieve the stable electron arrangement
3. Hydrogen atom, H contribute one electron each for sharing
Explain the formation of hydrogen molecule
-
1. Hydrogen atom, H with the electron arrangement 1
2. Hydrogen atom, H has one valence electron
2
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Double covalent bonds
• A covalent bond formed when a 2 pair of electrons is shared between two atoms
Lets investigate the formation of oxygen molecule
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2.6
+
2.6
2.8 2.8
O O
O O
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5. A double covalent compound with formula O is formed
4. Two oxygen atom share 2 pairs of electron to achieve the stable electron arrangement
3. Oxygen atom, O will contribute 2 electron each for sharing
Explain the formation of oxygen molecule
-
1. Oxygen atom, O with the electron arrangement 2.6
2. Oxygen atom, O has 6 valence electron
2
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Triple covalent bonds
• A covalent bond formed when a 3 pair of electrons is shared between two atoms
Lets investigate the formation of nitrogen molecule
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2.5
+
2.5
2.8 2.8
N N
N N
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5. A triple covalent compound with formula N is formed
4. Two nitrogen atom share 3 pairs of electron to achieve the stable electron arrangement
3. Nitrogen atom, N will contribute 3 electron each for sharing
Explain the formation of nitrogen molecule
-
1. Nitrogen atom, N with the electron arrangement 2.5
2. Nitrogen atom, N has 5 valence electron
2
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7. A covalent compound with formula H O is formed
6. Two hidrogen atom share 1 pairs of electron with 1 oxygen atom to achieve the stable electron arrangement
5. Oxygen atom, O contribute 2 electron for sharing
Explain the formation of water molecule
1. Hydrogen atom, H with the electron arrangement 1
4. Hidrogen atom, H contribute 1 electron for sharing
2
2. Oxygen atom, O with the electron arrangement 2.6
3. The valence electron of hydrogen atom, H is 1 and oxygen atom, O is 6
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O H H
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Explain the formation of:
-
1. Carbon dioxide molecule
4 2. Methane, CH
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Properties of Ionic and Covalent Compounds
Ionic Compound
Exist as solid at room temperature
High melting and boiling points
Conduct electricity in aqueous solution or molten state
Dissolve in water BUT do not dissolve in organic solvents
Covalent Compound
Exist as solid, liquids or gases
Low melting and boiling points
Do not conduct electricity at any state
Dissolve in organic solvents BUT do not dissolve in water
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Electrical conductivity
• In solid state, ions do not move freely. Hence, ionic compound does not conduct electricity in solid state
• In aqueous or molten state, ions are free to move. Hence, the compound can conduct electricity
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Electrical conductivity
• A covalent compound consist of neutral molecules
• There are no free moving ions in covalent compound
• Hence, covalent compounds do not conduct electricity at any state
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Melting and boiling points
• Ionic compounds are held together by strong electrostatic forces
• More heat energy is needed to overcome the strong forces
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Melting and boiling points
• Covalent compounds are held together by weak intermolecular forces
• Less heat energy is needed to overcome the weak forces