Chemistry - Unit 1

Atomic Structure - electron shells have 2 electrons in the first shell and 8 in the rest. Nucleas contains protons and neutrons. Electrons are negative, protons are positive and neutrons arent charged. Electrons and protons are the same number.

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Bonding

Ionic Bonding is between metals and non-metals and is transfer of electrons.

OIL - Oxidation Is Losing electrons RIG - Reduction Is Gaining electrons.

Ions are charged particles.

Covalent Bonding is between a non-metal and non-metal and produce covalent bond which are held together by shared electrons.

DIATOMIC MOLECULES

Metallic Bonding is between metals and metals. They have delocalised electrons and the strong electrostatic attraction bonds the metals together.The delocalised electrons act like a glue, they can also conduct electricity, slide over each other to make the metal malleable.

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Molecules and Compounds

Ionic Compounds are arranged in a lattice. The electrostatic force between the oppositely charged ions act in all direction and they are also very strong, this hold the lattice together very tightly.

Many ionic compounds will dissolve in water. When we disssolve an ionic compound in water the lattice is split up by the water molecules, and the ions are free to move. In the same way as molten ionic compounds will conduct electricty because the ions in the solution are able to move around.

Simple Covalent Molecules are very strong so the atoms within each molecule are held very tightly together. However, each molecule tends to be quite sperarate from its neighbouring molecules. The covalent compounds have weak intermolecular forces. COVALENT COMPOUND HAVE NO CHARGE = CANNOT CONDUCT ELECTRICITY

Giant Covalent Structures - unlike simple molecular structures, when a giant covalent structure melts or boils, the covalent bonds break. They have very high melting and boiling points and they dont conduct electricty(except graphite).

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Nanoscience

Nanoscience is a new branch of science that refers to the structures built from a few hundred atoms and are 1 to 100nm big. They have different properties to larger substances.

A Fullerene is a molecule made of carbon atoms that form a holow cage like structure. The arrangement of the atoms make pentagonal and hexagonal shapes. The smallest fullerene has 23 atoms. The Buckminster Fullerene, or buckyball, has 60 carbon atoms and forms the shape of a ball with carbon atoms at each corner of the 20 hexagons and 12 pentagons. THEY CAN CONDUCT ELECTRICTY

 

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Polymers

Polymers are long chained molecules made many monomers. The properties of polymer depends on; a) The monomer making them up, and b) The way the monomers are arranged.

LD Polymers are spaced out and random.

HD Polymers are uniform and packed together tightly.

Pressure, temeperature and catalysts affect the arrangement of bond.

There are two categories of Polymers;
A) Thermosoftening Polymers whose chains are tangled up. These polymers soften when heated and reset when cooled down.

B) Thermosetting Polymers these have strong covalent bonds forming crosslinks between polymer chains giving very high melting points and very high boinling points, e.g. kettle.

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