Chemistry IE

Every thing that i have learnt in topic IE. Ions and Electrolysis.

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  • Created by: ruaridh
  • Created on: 22-12-11 07:05

Key words.

Anion (an-ion): A negative ion. So-called becasue it is attreacted to the positive anode.

Anode: In elelctrolysis the anode is the positive electrode. Oxidation, loss of electrons, occurs at the anode.

Atomic number (proton number); The number of protons in the nucleus of an atom or ion.

Cathode: IN electrolysis the cathode is the negative electrode. Reduction, gain of electrons, occurs at the cathode.

Cation (Cat-ion): A positive ion. So-called becasue it is attracted tot eh negative cathode.

Discharge: When ions reach an electrode an lose or gain electrons (turning back into an elelment) they are said to be dischared.

Electrode: A condutor which dips into the electrolyte of and electrolytic or electromchemical cell and alloes the current (electrons) to flow.

Electron:  A negatively chared particle found in the shells of an atom. Its mass is approximately 1/2000 that of a proton or neutron.

Electrolysis:  A process in which chemical decomposition of a substance, known as the electrolyte, is caused by the passage of an electric current.

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Electrolyte: An electrolyte is an ionic compound, a salt, alkali or acid, which will conduct electricity when it is melted or dissovled inwater. An electrolyte will not conduct electricity when solid.

Group: A vertical divistion in the periodic table. Elements in the same group have similar chemical properties since they have the same nubmer of electrons in their outer shell or valence shells.

Migration: The movement of ions through and electrolyte.

Neutron: A neutral sub-atomic particle found in the nucleus. Its mass is 1 atomic mass unit.

Nucleon number: The number of protons and neutrons in the nucleus.

Oxidation: Oxidation involves the addition of oxygen or loss of hydrogen.

Period: A horizontal row on the periodic table. The periodoic table is so-named becayse the properties of elements repeat peridocially.

Proton: A positiverly chared sub-atomic particle located in the nucleus of an atom. Its mass is 1 atomic mass unit.

Redox Reaction: A reaction involving reduction and oxidation and which results in one or more electrons are transferred.

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Reducing agent: A chemical or substance that brings about reducing; it donates electrons to the reactant or one of the reactants. In the reaction the reducing agent itself is oxidised.

Reduction: Reduction involves the removal of oxygen or addition of hydrogen.

Shell (Energy leverl): A region surronding the necleus of an atom in which electrons are likely to be found.

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IE 1: Inside the atom.

The nucleus of and atom contains protons and neutrons. The general name for protons and neutrons is nucleons. Protons have a positive charge but neutrons have no charge. Outside the nucleus are the electrons, which are negatively charged. The electrons are arranged in shells or energy levels. THe number of protons in an atom is equal to the number of electrons.

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IE 2: Ions and ionic bonding.

How is and ion formed: An ion is abd electricall charged particle. Ions are formed when atoms lose or gain one ore more electrons. One way of gaining a full outer shell of electrons is by completely transferring outer shelll electrons from one atom to another.

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IE 3: Ionic Bonding and Giant ionic Lattices

More about ionic bonding: In ionic bonding the attractive forces between the positive and negative ions result in the formation of a gaiant ionic structure. The ions are regularly arranged in the crystal. This arragment carries on in three dimensions throughout the crystal. This three-dimensional network is called a crystal lattice. The electrostatic attractive forces between the ions act in all directions and are very strong. It takes a lot of energy to overcome these forces. This is why diant ionic structures have high melting/ boiling points.

Molecules: The covalent bonds within molecules are very strong. However, the forces between the separate moelcules are weak. These weak forces are call Intermolecular forces. because of these forces between molecules are weak it onlu meed a little energy to overcome these forces and get the molecules to move away form each other. This is why molecular substances have low melting poins and boiling points.

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IE 4/5: Electrolytes and Electrolysis

Metal ions are positive. They migrate to the negitive cathode.

Non-metal ions are negative. They migrate to the positive anode.

 The periodic talbe tells us the charge of each ion:

Group 1 = 1+                         Group 6 = 2-

Group 2 = 2+                         Group 7 = 1-

Group 3 = 3+

Elecrolysis occures when a electic current passes through a molten electrolyte. The two rods dipping into the electrolyte are called electrodes. Metals are deposited at the Cathode and non-metal are formed at the anode.

During Electrolysis positive ions move toward the Catode and the negative ions move toward the anode, At the cathode the metal or oxygen ions gain electrons and for metal atoms or hydrogen gas. At the anode the non-metal ions lose electrons and form halogens or hydrogen.

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IE 6: Extracting Aluminium

Aluminium is extracted by the electrolysis of molten aluminium oxide cryolite in dissolved. This mixture melts at a much lower tempuatre than pure aluminium oxide. Therefore a lot of energy is saved and the electrical conductivity of the electrolyte is improved.

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