Giant ionic and giant covalent structures

What are giant ionic solids made out of?

oppositely charged ions packed around each other.

How does giant ionic solids ensure maximum energy?

• packed around each other - maximises electrostatic attraction between oppositely charged ions and minimises repulsion

What is the crystal coordination number of sodium chloride?

6:6

What is the crystal coordination number of caesium chloride?

8:8

Why is there a difference in coordination number in Cs than Na?

Cs⁺ cation is larger than that of Na⁺, so has more room to accommodate a greater number of anions.

What are the properties of ionic compounds?

• high melting boiling point

• electrical insulators - doesn’t conduct electricity

• brittle and hard

• certain compounds soluble in water

Why do ionic compounds have high melting points?

strong electrostatic attraction between the oppositely charged ions, which requires a lot of energy to overcome.

Why are ionic compounds conduct electricity when molten or dissolved?

conduct due to the ions being free to move and carry a charge when voltage is applied.

Why are ionic compounds brittle?

due to repulsion between like charged ions when the layers of ions are shifted by a large enough force.

Why are certain ionic compounds soluble in water?

• solid dissolves - ions surrounded by water - attracted to ions due to water molecules having permanent dipoles

How does a giant covalent structure form a diamond?

each carbon bonds strongly to four other carbon atoms in a tetrahedral arrangement to form a giant 3D structure.

How does graphite form?

only three bonds are made by each carbon atom. Hexagonal layers are formed, which are held together by weak van der Waals forces.

What are some similarities in diamond and graphite?

• both high melting points and boiling points - strong covalent bond - lots of energy to overcome

• insoluble in water - no charged particles capable of interacting with permanent dipole of water molecules

What’s are properties specific to diamond?

• hard - due to each carbon bonded to others - strong covalent bond

• electrical insulator - no delocalised electrons within structure to carry charge

What are some properties specific to graphite?

• soft and slippery - layers of carbon atoms - weak intermolecular forces - slide over each other

• electrical conductor - one non-bonding electron in valence shell of each carbon atoms - become delocalised between layers