Topic 2 Flashcards
1
Q
Formation of Ions
A
- When metals form ions they loose electrons from their outer shell to form positive ions
- when non-metals form ions they gain electrons into their outer shell to form negative ions
- the number of electrons lost or gained is the same as the charge on the ion
2
Q
Ionic bonding
A
- Transfer of electrons when a non-metal and metal reacts
- non-metal forms gains electrons to become negative and metal looses electrons to become positive
- these oppositely charged ions are strongly attracted to one another by electrostatic forces, this attraction is called an ionic bond
- dot and cross diagrams show how ionic compounds are formed
3
Q
Ionic compound
A
- giant ionic lattice structure
- strong electrostatic forces of attraction between oppositely charged ions in all directions in lattice
- high melting and boiling points due to strong bonds between the ions and takes lots of energy to overcome attraction
- when solid the ions are held in place so compounds cannot conduct electricity, when ionic compounds melt, ions are free to move and they’ll carry electric current
- some ionic compounds dissolve in water, ions separate and are free to move in solution so carry electric current
4
Q
Covalent bonding
A
- non-metal atoms bond together, they share pairs of electrons to make covalent bonds
- positively charged nuclei bonded atoms are attracted to the shared pair of electrons by electrostatic forced making covalent bond very strong
- atoms only share electrons in outer shells (highest energy levels)
- each single covalent bond provides one extra shared electron for each atom
- each atom involved makes enough bonds to fill outer shell, having outer shell gives the electronic structure of a noble gas, which is stable
- covalent bonding in compounds of non-metals and in non-metal elements
5
Q
Simple Molecular Substances
A
-made up of molecules containing a few atoms joined together by covalent bonds
Example:
Hydrogen, Methane, Chlorine, Nitrogen, Oxygen, Water, Hydrogen chloride
6
Q
Properties of simple molecular substances
A
- held together by strong covalent bonds
- forces of attraction between bonds are weak
- feeble intermolecular forces
- low boiling points because molecules are easily parted from each other
- most are gases and liquids at room temperature
- as molecules get bigger the intermolecular forces are stronger so it takes more energy to break them and the melting and boiling point increases
- they do not conduct electricity as no free electrons or ions
7
Q
Polymers
A
- long chains of repeating units
- intermolecular forces are larger than the forces between simple covalent molecules
- solid at room temperature
- intermolecular forces are weaker than ionic and covalent bonds
8
Q
Giant Covalent structures
A
- macromolecules
- all atoms are bonded together by strong covalent bonds
- high melting and boiling points as lots of energy is needed to break them
- don’t conduct electricity as no charged particles (not even when molten)
9
Q
Allotropes of carbon
A
10
Q
Diamond
A
- giant covalent structures made up of carbon atoms that each form four covalent bonds
- hard
- high melting and boiling point as take a lot of energy to break
- does not conduct electricity as no free electrons or ions
11
Q
Graphite
A
- contains sheets of Hexagons
- each carbon atoms forms three covalent bonds creatin sheets of carbon atoms arranged in hexagons
- layers have no covalent bonds and are held together weakly, so they are free to move over each other and this makes graphite slippery and soft so ideal as lubricating material
- high melting point
- one delocaised electron so conducts electricity
12
Q
Graphene
A
- one layer of graphite
- a sheet of carbon atoms joined together in hexagons
- one atom thick, making it a two-dimensional substance
- strong and incredibly light
- contains delocaised electrons so conducts electricity
13
Q
Fullerenes from spheres and tubes
A
- molecules of carbon
- shaped like closed tubes or hollow balls
- mainly made up of carbon atoms arranged in hexagons but also contain pentagons or heptagons
- fullerenes can be used to ‘cage’ other molecules - deliver drug into body
- large surface area - industrial catalysts
Fullerenes can form nanotubes (tiny carbon cylinders) - ratio is high
- conduct thermal heat and electricity
- high tensile strength
- technology that uses small particles such as nanotubes is called nanotechnology
uses: - deliver drug into the body
- industrial catalysts
- lubricants
- nanotubes can be used in electronics or to strengthen material without adding much weight
14
Q
Metallic bonding
A
- giant structures
- outer shell electrons of the metal atoms are delocalised
- strong forces of electrostatic attraction between positive metal ions and the shared negative electrons
- forces of attraction hold atom together in regular structure and are known as metallic bonding
15
Q
properties of metallic bonding
A
- solid at room temperature
- malleable (slide over each other)
- high melting and boiling point
- good conductors of electricity
