3.1.3 Bonding Flashcards
What are Compounds?
Compounds are Atoms of different Element Bonded together
What is Ionic Bonding?
When Ions are held together by Electrostatic Attraction
How are Ions formed?
Ions are formed when one or more electrons are transferred from one atom to another
Why does Sodium Chloride have a ‘Giant Ionic Lattice’ structure?
1) Ionic crystals are giant lattices of ions. A lattice is just a regular structure
2) Structure’s called ‘giant’ because its made up of the same basic unit repeated over and over again
3) In Sodium Chloride, the Na+ and Cl- ions are packed together. The Sodium Chloride lattice is Cube shaped – different ionic compounds have different shaped structures
How does Ionic Structure explain the Behaviour of Ionic Compounds?
1) Ionic Compounds conduct electricity when they’re molten or dissolved, but not when solid – Ions in liquid free to move. In solid they are fixed in position by strong ionic bonds
2) Ionic Compounds have high melting points – Giant ionic lattices held together by strong electrostatic forces. Takes lots of energy to overcome this hence high melting points (e.g 801˚C for Sodium Chloride)
3) Ionic compounds tend to dissolve in water – water molecules are polar, part of molecule slightly negative and other slightly positive. Charged parts pull ions away from Lattice, causing it to dissolve
What are molecules?
Molecules are Groups of Atoms Bonded Together
How are Molecules formed?
Form when two or more atoms bond together – it doesn’t matter if the atoms are same or different.
e.g. Cl2 (Chlorine Gas), CO (Carbon Monoxide), H2O (Water) and C2H5OH (Ethanol)
What hold molecules together?
Strong Covalent bonds
What does a single covalent bond contain?
A Shared Pair of Electrons
What do Giant Covalent structures have?
A Huge Network of Covalently bonded atoms (sometimes referred to as macromolecular structures)
Why is Carbon an example of Giant Covalent Structures?
Because they can each form 4 strong, covalent bonds.
What is Graphite?
An example of a Carbon Macromolecule with sheets of Hexagons with Delocalised Electrons
How does the structure of Graphite explain its properties?
1) Weak bonds between layers in graphite are easily broken, so sheets can slide over each other – graphite feels slippery so is used as a dry lubricant and in pencils
2) ‘Delocalised’ electrons aren’t attached to particular carbon atom and are free to move along the sheets carrying a charge. So Graphite is an electrical conductor
3) The layers are quite far apart compared to length of covalent bonds, so graphite has low density and used to make strong, lightweight sports equipment
4) Because of strong covalent bonds in hexagon sheets, graphite has very high melting point (sublimes @ over 3900K)
5) Graphite is insoluble in any solvent. Covalent bonds are too strong to break
What is Diamond?
Hardest Known Structure. Made up of Carbon atoms. Each Carbon Atom is covalently bonded to four other Carbon atoms. Atoms arrange themselves into tetrahedral shape
How does the Structure of Diamond explain its properties?
1) Very high melting point – sublimes @ over 3900K
2) Extremely hard – used in diamond-tipped drills and saws
3) Vibrations travel easily through stiff lattice, so its a good thermal conductor
4) Can’t conduct electricity – all outer electrons are held in localised bonds
5) Won’t dissolve in ANY Solvent (Insoluble)
6) You can ‘cut’ Diamond to form gemstones. Its structure makes it refract light a lot, which is why it sparkles
