Bonding, Structure, and The Property of Matter

What is ionic bonding ?

The electrostatic attraction between positive and negative ions, it is a rekativdlg string attraction.

How are ionic compounds held together ?

• Held together in a giant lattice

• A regular structure that extends in all directions in a substance

• Electrostatic attraction between positive and negative ions holds the structure together

What are the properties of ionic substances ?

• High melting and boiling point (strong electrostatic forces between oppositely charged ions)

• Do not conduct electricity when solid (ions in fixed positions)

• Conduct when molten or dissolved in water - ions are free to move

How are ionic compounds formed ?

Reaction of a metal with a non-metal, electron transfer occurs and metal gives away its outer shell electrons to a non-metal

What is a covalent bond ?

A shared pair of electrons between two atoms.

What is the structure and properties of simple molecular covalent substances ?

• Do not conduct electricity

• Small molecules

• Weak intermolecular forces

• Low melting and boiling points

How do intermolecular forces change as the mass of the molecule increases ?

Increases which causes the melting/boiling points to increase as well because more energy is needed to overcome these forces

What are polymers ?

Large molecules with atoms linked by covalent bonds

What are thermosoftening polymers ?

They melt/soften when heated, there are no bonds between polymer chains and the weak intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts.

What are giant covalent substances ?

• Solids, atoms covalently bonded together in a giant lattice

• High melting/boiling points - strong covalent bonds

• Mostly don’t conduct electricity (no delocalised electrons)

  
  

What are the properties of carbon ?

• Four strong covalent bonds for each carbon atom

• Very hard - strong bonds

• Very high melting point - strong bonds

• Does not conduct - no delocalised electrons to carry charge

What are the properties of graphite ?

• Three covalent bonds for each carbon atom

• Layers of hexagonal rings

• High melting point - strong bonds

• Layers free to slide as weak intermolecular forces between layers

• Conduct thermal and electricity due to one delocalised electron per each carbon atom

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What are the properties of fullerenes ?

• Hollow shaped molecules

• Based on hexagonal rings but may have carbon rings

• Has a spherical shape, simple molecular structure

Why is buckministerfullerene a good lubricant ?

Low friction due to the spherical shape and their size which allows them to roll into tiny spaces between surfaces

What are the properties of nanotubes ?

• Cylindrical fullerene with high length to diameter ratio

• High tensile strength - high number of covalent bonds

  • Thermal and electricity conductors - delocalised electrons carrying charge

What are the properties of graphene ?

• A single layer of graphite

• Conduct heat and electricity due- delocalised electrons

• Very thin - only one atom in thickness

• Strong - made up of many covalent bonds

What is metallic bonding ?

Forces if attraction between delocalised electrons and nuclei of metal ions.

What are the properties of metals ?

• High melting and boiling points - strong forces of attraction

• Good conductors of heat and electricity - delocalised electrons

• Malleable, soft - layers of atoms can slide over each other whilst maintaining the attraction forces

What are the properties of metals ?

• High melting and boiling points - strong forces of attraction

• Good conductors of heat and electricity - delocalised electrons

• Malleable, soft - layers of atoms can slide over each other whilst maintaining the attraction forces

Why are alloys harder than pure metals ?

Different sizes of atoms distorts the layers so they can’t slide over each other

What is the structure of a metal ?

Atoms in a metal are tightly packed together in layers which form a regular metallic lattice structure within a sea of delocalised electrons

What is the structure of a metal ?

Atoms in a metal are tightly packed together in layers which form a regular metallic lattice structure within a sea of delocalised electrons

What are the limitations of the dot and cross diagrams?

Shows how ionic compounds are formed but don’t show structure of the compound or the relative sizes of the ions

What are the limitations of 3D models ?

Shows relative size and regular pattern however only shows the outer layer of the compound

What are the limitations of the ball and stick models ?

Show regular patterns in ionic lattice and how all ions are arranged, however ions are not shown to scale and show gaps when there are none in reality

What are the limitations of the simple model ?

There are no forces between spheres and atoms, molecules and ions are solid spheres which is not true

What are the uses of nanoparticles ?

• Medicine

• Electronics

• Deodorants

Why do nanoparticles have properties different from those for the same materials in bulk ?

High surface area to volume ratio