it is ductile and malleable, which are useful properties
only forms 3 covalent bonds, so slides easily, conducts electricity and high melting point
strong covalent bonding, allows very high melting points
7. Describe metallic bonding
strong electrostatic attraction between closely packed positive metal ions and the 'sea' of delocalised free electrons
strong bonds between atoms that requires lots of energy to break
strong electrostatic attraction between closely packed negative metal ions and the 'sea' of delocalised free electrons
strong forces of electrostatic attraction between positive nucleus and surrounding bonded negative electrons
8. What determines a Thermosoftening polymer?
made up of chains that are held up by weak intermolecular forces and slide easily over each other. This means it stretches easily and has a low melting point
held together by weak forces between chains, so it can easily melted down and remoudled
Lack of cross-links and use of weak low-chain plastics
made up of chains that are held up by strong intermolecular forces and slide easily over each other. This means it stretches easily and has a low melting point
9. What is the stationary phase in TLC (Thin-layer chromatography)?
thin layer of solid e.g. silica gel
ink
heated ceramic
copper oxide powder
10. Why are covalent bonds so strong
strong inter-molecular forces
strong forces of electrostatic attraction between positive nucleus and surrounding bonded negative electrons
Has a closely packed regular lattice with strong forces of electrostatic attraction between oppositely charged ions
11. What is the mobile and stationary phase for GC
mobile phase - solvent. stationary phase - silica gel
mobile phase - unreactive gas (nitrogen). stationary phase - viscous liquid (oil)
mobile phase - argon gas. stationary phase - sodium chloride
12. Why do ionic compounds have high melting and boiling points?
Strong, stable bonds between molecules
Has a closely packed regular lattice with strong forces of electrostatic attraction between oppositely charged ions
Strong electrostatic attraction between positive nuclei of a atom and negative electrons
Has a closely packed regular lattice with strong forces of electrostatic repulsion between oppositely charged ions