IONIC, COVALENT, & METALLIC BONDING
Chemical Bonding - The force that holds atoms in a molecular bond.
1) Ionic - Electrostatic forces of attraction between oppositely charged ions
2) Covalent - When a pair of electrons are shared by two adjacent atoms
3) Metallic (all metals are cations) - The electrostatic force of attraction between positive metal ions and a sea of delocalized mobile electrons.
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Ionization energy - Minimum amount of energy required by an atom to remove the valence electron from its orbit.
Oxidation - Loss of electrons or increase in oxidation number (E.g. Mg^0 --> Mg^+2)
Electron Effinity - The energy changes that occur when an atom gains electrons.
Electrostatic forces of attraction - Attraction between opposite ions which binds them together.
Figure 2. Dot and Cross Diagram Examples
Ionic Bonding
- Between metals (Group 1 & 2) and non metals (Group 5, 6 & 7)
- Giant Lattice Structure
- Dot and Cross Diagram used
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PHYSICAL PROPERTIES
- High melting and boiling points
- Non-volatile
- Soluble in water
- Insoluble in organic solvents
- Can conduct electricity in molten and aqueous state (free electrons present and not bound in giant lattice structure)
Figure 1. Giant Lattice Structure
Figure 3. Covalent and Ionic Bonding Difference
Covalent Bonding
- Sharing of electrons, molecules formed
- Between non-metals, same and different elements
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Terms:
- Mono: 1
- Di: 2
- Tri: 3
- Tetra: 4
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SIMPLE MOLECULAR STRUCTURES
- Low melting and boiling points
- Usually volatile liquids and gases
- Soluble in organic solvents
- Insoluble in water
- Do not conduct electricity in liquid, gas or solid state
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GIANT MOLECULAR STRUCTURES
- High melting and boiling points
- Do not conduct electricity (except graphite)
- Insoluble in organic solvents and water
WRITING IONIC EQUATIONS
1) Write a balanced equation with state symbols
2) Write the elements of ONLY aqueous solutions as ions
3) Cross out those ions which remain in the same form on both sides (aq)
4) Re-write equation neatly.
Figure 4. Molecular structure of diamond
Figure 5. Molecular structure of graphite
Figure 6. Formation of 2 single covalent bonds in water
Metallic Bonding
Figure 7. Triple covalent bond in nitrogen gas
- Simple molecular structure
Metallic Bonds: Alloys & Metals
- The strength of a metallic bond depends on two things:
1) Size. If the size of particles in the bond are small, the bond is stronger
2) Charge. If the charges on the particles are large, the bond is stronger
*** The weaker the bond, the lower the melting and boiling points
- In a metallic bond, all the metal atoms lose their outer electrons and become cations. They are held by strong electrostatic forces of attraction in a sea of delocalized electrons (the lost electrons from the metals).
- Giant lattice structure
PROPERTIES:
- Malleable (Hammered into shapes- metal ions slide to one side through sea of electrons)
- Ductile (Drawn into wires)
- Good heat conductors
- High density
- High boiling and melting point
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Figure 8. Metallic bonds