MYP Chemistry Structure and Bonding Notes

Chemical Bonding: How Electrons Hold Substances Together

At the heart of chemistry is a simple idea:

Chemical bonds form when atoms transfer or share electrons to achieve more stable electron configurations.

There are three main types of bonding you need to understand at this level:

1. Ionic bonding – electrons are transferred
2. Covalent bonding – electrons are shared
3. Metallic bonding – electrons are delocalised (a “sea of electrons”)

These bonding types, plus the way particles are arranged in space, explain why substances have such different properties (like melting point, conductivity, hardness, solubility, etc.).

Ionic Bonding – Electron Transfer and Giant Lattices

How Ionic Bonds Form

1. The metal loses one or more electrons → forms a positive ion (cation).
2. The non-metal gains those electrons → forms a negative ion (anion).
3. Oppositely charged ions are held together by strong electrostatic attraction.

Structure: Giant Ionic Lattice

1. Ionic compounds (like NaCl, MgO) don’t form single “molecules”.
2. Instead they form a giant ionic lattice:
   1. Every Na⁺ is surrounded by six Cl⁻.
   2. Every Cl⁻ is surrounded by six Na⁺.
   3. Positive and negative ions alternate in a regular 3D structure.
3. This maximizes attraction and minimizes repulsion.

How Structure Explains Ionic Properties

1. Very high melting and boiling points
   1. Strong electrostatic forces in the lattice require a lot of energy to break.
2. Electrical conductivity
   1. Solid: does not conduct – ions are fixed in place.
   2. Molten (liquid) or aqueous (dissolved in water): does conduct – ions are free to move and carry charge.
3. Brittle
   1. If layers are forced to slide, ions of the same charge may be pushed next to each other → repel → lattice shatters.
4. Often soluble in water
   1. Water is polar and can surround and separate ions (hydration), pulling them away from the lattice.

Covalent Bonding – Sharing Electrons and Simple Molecules

How Covalent Bonds Form