Giant Covalent And Metallic Structures

Question 1

What holds the atoms together in giant covalent structures?

Answer 1

Electrostatic attractions

Question 2

What are 2 common examples of giant covalent networks and why can they form these structures?

Answer 2

Carbon and silicon because they can each form 4 strong covalent bonds

Question 3

What arrangement is carbon in as a giant covalent network?

Answer 3

Tetrahedral

Question 4

What are the 5 common properties of covalent networks and why do they have these?

Answer 4

1. Very high melting points - you need to break a lot of very strong bonds before the substance melts, which takes a lot of energy
2. Are often extremely hard - very strong bonds all through the lattice arrangement
3. Are good thermal conductors - vibrations travel easily through stiff lattices
4. Won’t dissolve - the covalent bonds mean atoms are more attracted to their neighbours in the lattice than to solvent molecules. The fact that they are all insoluble in polar solvents like water shows they don’t contain ions
5. Can’t conduct electricity- since there are no charged ions or free electrons (except in graphite, where there is only 3 bonds per carbon atom, leaving the other as a delocalised electron)

Question 5

What is metallic bonding?

Answer 5

The positive metal ions are attracted to delocalised negative electrons, they form a lattice of closely packed positive ions in a sea of delocalised electrons

Question 6

What are the 5 common properties of metals and why do they behave this way?

Answer 6

1. Generally high melting points - strong metallic bonding (number of delocalised electrons, size of the metal ion and the lattice structure affects mp)
2. Can be shaped and are ductile - no bonds holding specific ions together, so metal ions can slide over each other when the structure is pulled
3. Good thermal conductors - delocalised e can pass kinetic energy to each other
4. Good electrical conductors - delocalised e are free to move and carry a charge, any impurities can dramatically reduce the electrical conductivity by reducing the number of free electrons
5. Insoluble (except in liquid metals) - strong metallic bonds