BONDING, STRUCTURE AND STATES OF MATTER

Ionic bonding

• An ion is a charged particle, which is formed when elements gain or lose electrons to gain a full outer shell

• Elements are more likely to form ions if there are not many electrons lost or gained

  • Takes less energy

  • Groups 1,2,6 and 7 are most likely

  • Groups 3,4 and 5 are rarely seen as ions

• Happens between a metal and non-metal

• For example, Na$\rightarrow$Na⁺ + e^- and Cl + e^- $\rightarrow$ Cl^-

• Electrons are transferred

• NaCl becomes an ionic compound and are attracted by strong electrostatic forces (have opposite charges)

Ionic compounds

• Metals and non-metals form ionic compounds with strong electrostatic forces and ionic bonds

• Usually group in large numbers

  • Regular lattice structures (3D)

  • Each ion is attracted to all those around it

• Properties - very high melting points as lots of energy is required to overcome strong ionic bonds

  • can conduct electricity when molten or aqueous as charged particles are free to move

• NEED TO KNOW - Hydroxide = OH^-

  • Sulphate = SO₄^-

  • Nitrate = NO₃^-

  • Carbonate = CO₃^-

  • Ammonium = NH₄⁺

Covalent bonding

• The sharing of electrons in the outer shell between non-metals to gain a full outer shell

• Cl - Cl

  

• They can become:

  • Simple molecular substances - Small molecules with strong covalent bonds between atoms and weak intermolecular forces between molecules

    • Like water, ammonia, chlorine or methane

  • Polymers - Long chains of repeating units (monomers)

  • Giant covalent structures - diamond, graphite + silica dioxide

Metallic bonding

• Happens between metal atoms

• Solid metals are in a giant structure arranged in a regular pattern with delocalised electrons

  • They give up their outer shell electrons and share them with the other metals

  • The atoms all become + ions

  • The lost electrons can freely move so are delocalised

  • There are strong forces of attraction between the ions and electrons, which hold everything together in a regular structure

• Metals are strong, so have high melting and boiling points

• They are good conductors of heat and electricity ⚡

  • Their delocalised electrons can feely move and carry electrical current through the structure

• Metals are malleable - their regular structure allows layers to slide

• Alloys are when 2 or more different metals or a metal and non-metal form metallic bonds, with different sized atoms

  • This disrupts the regular structure, so layers can no longer slide

• Alloys are stronger than pure metals

States of matter

• Solids - Strong forces of attraction (holds them close together)

  • Fixed, regular position

  • Definite shape and volume - can vibrate

• Liquids - Weak forces of attraction (particles are free to move and flow)

  • Can flow

  • Compact and definite volume, but not shape

  • Move to fit a container

• Gas - Very very weak forces of attraction

  • No definite shape of volume

  • Fill a container

  • Particles are free to move

  • Constantly moving with random motion - move in a straight line and are deflected when hit

State symbols

• Solid - s

• Liquid - l

• Gas - g

• Aqueous - aq

Properties of ionic compounds

• High melting and boiling point

  • Lots of energy is required to overcome strong electrostatic forces of attraction, and there are lots of forces

• Can conduct when aqueous or molten

  • Charged particles are free to flow through the structure

Properties of small molecules

• Low melting and boiling points

  • Weak intermolecular forces between molecules, that need little energy to break

  • COVALENT BONDS ARE NOT BROKEN

• Generally liquids or gases at room temperature

• Do not conduct

Properties of metals and alloys

• Metals are soft and malleable, shiny, good conductors of heat and electricity and have high melting and boiling points

• Alloys are hard (no layers), have high melting and boiling points and are good conductors

Giant covalent structures

• Simple molecular substances have low melting points, strong bonds between atoms and don’t conduct

• Giant covalent structures have huge numbers of non-metal atoms

  • Arranged in a regular repeating lattices

  • Have high melting and boiling points as there are a lot of covalent bonds

  • Very strong - lots of bonds

  • Generally don’t conduct (apart from graphite and graphene)

• Silica dioxide is made of silicon and oxygen in a ration of 1:2

  • Makes up sand 🏖

Diamond and graphite

• Allotropes of carbon

• Diamond is a giant covalent structure💎

  • Is very strong

  • Each carbon is bonded to 4 other carbons (max amount)

  • It doesn’t conduct as there are no delocalised electrons

• Graphite is a giant covalent structure

  • Is very strong

  • Each carbon makes 3 out of 4 covalent bonds possible

  • Is arranged in layers with weak intermolecular forces between them

    • This allows the layers to slide over one another and makes it soft

  • Has a high melting and boiling point

  • Can conduct electricity - only ¾ bonds are made, so there are left over electrons

    • Become delocalised (one per carbon atom) and are free to move through the structure and carry charge

• Graphene is a single layer of graphite

Graphene and fullerenes

• Are allotropes of carbon

• Graphene is a single layer of graphite and can conduct electricity as there are delocalise electrons

  • Useful in electronics (conducts and is small)

• Fullerenes are tubes and spheres made out of a single sheet of graphite

  • Spheres can be used to surround molecules (like drugs) and used to deliver to specific areas of the body

  • They have a large surface area : volume ratio, so make good industrial catalysts

  • Tubes can be used in nanotechnology as conductors, to strengthen tennis rackets (adds strength without weight as high length : diameter)

  • Buckminster fullerene is a hollow sphere that is made of 60 carbon atoms and is used for drug delivery

  • Using tiny structures is called nanotechnology

    • Medicine, fashion, batteries and food

Nanoparticles

• Nanoparticles are really really really tiny particles - 1nm - 100nm (0.00000001m)

• Nanoscience is produces new nanoparticle materials

• They have a large surface area : volume ratio

  • Good for catalysts as surface area increases its efficiency

  • Nanomedicine uses fullerenes to deliver drugs around the body

  • Electrical circuits use them to make tiny computer chips as some can conduct

  • Silver nanoparticles have antibacterial properties so can be infused into wound dressings and masks

• Issues with nanoparticles

  • They are relatively new so we are not aware of all risks (long term)

  • For example, sun cream with nanoparticles allows for better skin coverage but we are unaware if it can enter our body through the skin and potential damage cells

  • They are also possibly damaging to the environment

Sizes of particles and their properties

• Atoms and small molecules - 0.1 nm

• Nanoparticles - 1 to 100nm

• Fine particles - 100 to 2500 nm

• Coarse particles - 2500 to 10000 nm

• The smaller the particle, the higher the surface area : volume ratio, so increased reactivity

Polymers

• Polymers have very large molecules and their atoms are joined by strong covalent bonds in long chains

• Solid at room temperature

• Higher boiling points than strong intermolecular forces and lots of bonds to overcome

DONE!!!