Bonding , Structure and Properties Of Matter Flashcards
Formation of ions
Ions are charged particles. They can be single atoms or a group of atoms.
When metals form ions they lose electrons and become positive ions
When non metals form ions they gain electrons and become negative ions
Ionic bonding
Metal and non-metal
Metal loses electrons to form a positively charged ion and non metals gains these electrons to form a negatively charged ion
Dot and cross diagrams shows this
Ionic compounds
Giant ionic lattice. Have a regular lattice structure. Very strong electrostatic forces of attraction between oppositely charged ions.
High melting and boiling points
Can’t conduct electricity as when solid ions are held in place
When they melt the ions are free to move and carry electric charge
Some can dissolve in water
Covalent bonds
Sharing electrons
Non metals atoms bond together
Very strong bonds
Polymers
Polymers are long chains of repeating units
- strong intermolecular forces which means more energy is needed to break them so solid at room temp
- lower boiling points than ionic or giant molecular compounds
Giant covalent structures
Strong covalent bonds
Very high melting points
Mostly don’t conduct electricity (other than graphite)
Examples are diamond , graphite and silicon dioxide
Diamond - each carbon has 4 covalent bonds in a very rigid giant covalent structure
Graphite - each carbon forms 3 covalent bonds to create hexagon layers. Each carbon atom has one delocalised electron
Silicon dioxide - each grain of sand is one giant structure of silicon and oxygen
Allotropes of carbon
Diamond - very hard , strong covalent bonds , very high melting points , doesn’t conduct electricity , 4 covalent bonds per carbon
Graphite - 3 covalent bonds in hexagon layers , no bonds between layers so can slide making them soft / slippery , high melting point , conducts electricity
Graphene - single sheet of graphite , very strong , very light , can be added to composite metals to improve strength not hindering weight much , conducts electricity
Fullerenes - can be used to deliver a drug into body as they cage other molecules. Huge surface area so create catalysts. Can form nanotubes. Which :
Have a high length to diameter ratio
Conduct electricity and thermal energy
Have tensile strength ( don’t break when stretched)
Used in nanotechnology
Metallic bonding
Involves delocalised electrons with metal substances
Metal atoms with delocalised electrons surrounding them
Very high melting and boiling points due to strong electrostatic forces
Good conductors of electricity and heat
Malleable
Alloys - mixture of 2 or more metals - are harder than pure metals. It makes it harder for metal atoms to slide over each other as the atoms are different sizes so layers are distorted.
Nanoparticles and uses of nanoparticles
Very small
Large surface area to volume ratio
As particles decrease in size their surface area increases
Nano medicine , cosmetics like moisturiser , silver nanoparticles have antibacterial properties, some can conduct electricity
