Structure and Bonding - created from Mind Map

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Atomic Structure

The Atomic number and Mass number describe different features of an atom.

An isotope is: ' A different atomic form of the same element, with the same number of protons and electrons, but a different number of neutrons.'

Same atomic number- different mass number

Ionic Bonding

Transferring Electrons

Atoms lose or gain electrons to form charged particles (ions)- strongly attracted to each other

Group 1 and 2 metals only have to lose one/two electrons to become stable ions (+ charge)

Latch onto atoms that the gave/gained electron from

Elements in Groups 6 and 7 only have to gain one/two electrons to become stable ions (- charge)

Regular Giant Ionic Lattices

Very Strong electrostatic forces of attraction between oppositely charged ions in all directions

Ions and Formulas

Ions have the structure of a noble gas

Charges must balance each other e.g. MgCl2

Group 1 and 2 elements = metals - form + ions Group 1 elements( alkali metals) form ions with non metals where metal has 1+ charge

Group 6 and 7 elements = non-metals- gain electrons to form - ions Group 7 elements (halogens) form ionic compound with alkali metals where halide ion has 1- charge

Charge on positive ions is the same as group number e.g. Group 1 + LI+ Group 7 = F-

Groups 1,2,6 and 7 most readily form ions.

Properties

When molten, ions are free to move- will carry electric current

Dissolve easily in water. Ions separate- free to move- carry electric current

High melting and boiling points- strong attraction between ions

Covalent Bonding

Sharing electrons

Covalent Bond = shared pair of electrons

Dot and Cross diagrams

Simple Molecular Substances

Don't conduct electricity - no ions, no electrical charge

Most molecular substances are gases/ liquids at room temperature but can be solids

Intermolecular forces = very weak - Melting and boiling points are very lows - molecules easily parted

Very strong covalent bonds to form small molecules of several atoms.

Giant Covalent (Macromolecules)

Similar to giant ionic lattices except no charged ions

Don't conduct electricity- except graphite

All atoms bonded to each other by strong covalent bonds- very high melting/boiling points

Main examples = Diamond and Graphite

Diamond- Each carbon atom forms four covalent bonds in a v. rigid giant covalent structure. Diamond = hardest natural substance -used for drill tips

Graphite- Each carbon atom has 3 covalent bonds. Creates layers- free to slide over each other. Graphite soft and slippery. Layers can be rubbed off onto paper e.g. a pencil. Weak intermolecular forces between layers. Only non-metal that's a good conductor of heat and electricity. Delocalised electrons that conduct heat and electricity

Metallic Structures

Giant Structure

Metallic bonds involve 'free electrons'- come from outer shell of the metal atoms and produce the properties of metals

Electrons free to move- good conductors of heat and electricity

These electrons hold atom together in regular structure- strong forces of electrostatic attraction between + metal atoms and - electrons

Electrons allow layers of atoms to slide over each other - metals can be bent/shaped

Alloys are harder than pure metals-different sized atoms distorting layers- more difficult to slide over each other = harder

New Materials

Smart Materials

Behave differently depending on conditions e.g. temperature

Nitinol = shape memory alloy- when cool bends and twist like rubber. When heatedit goes back to a 'remembered' shape- used for braces

Nanoparticles

Between 1-100 nanometres across 1nm=0.000000001m

Contain roughly a few hundred atoms

Include fullerenes- molecules of carbon, shaped like hollow balls or closed tubes- arranged in hexagonal rings. Different fullerenes have different numbers of carbon atoms

A nanoparticle has v. different properties from the bulk chemical e.g. fullerenes have different properties from big lumps of carbon

Fullerenes can be joined together to make nanotubes. All the covalent bonds make nanotubes v. strong- Can be used to reinforce graphite in tennis rackets

Nanoscience

Huge surface area to volume ratio- could help make new catalysts

Nanotubes can make stronger, lighter building materials

Sun cream can include nanoparticles- do't leave white marks

Nanomedicine- fullerenes absorbed more easily by the body - could deliver drugs into the cells where they're needed

Nanotubes conduct electricity

Relative Atomic masses

Structure and Bonding