oxidation and reduction

• oxidation of an element takes place when it loses electrons
• an oxidising agent is a substance that brings about oxidation in other substances
• reduction of an element takes place when it gains electrons
• reducing agent is a substance that brings about reduction in other substances
• Oxidation


  Loses electrons
• relative molecular mass - the average mass of a molecule compared to 1/12th the mass of an atom of carbon-12
• mole- substances that contain 6x10^23 particles of that substance
• exited state - electrons occupy higher energy levels that those available in the ground state
• daltons atomic theory

  1.All matter is made up of very small particles called atoms

  2. All atoms are indivisible.They cannot be broken down into smaller particles
• ground state - the electrons occupy the lowest avaliable energy levels
• pink table
• mass number is the total number of protons and neutrons in an atom of an element
• medeleevs periodic law is that elements are arranged in order of increasing atomic weight
• Empirical formula

  Simplest whole number ratio of atoms in a compound
• Aufbau Principle


  Electrons fill tower-energy atomic orbitals before falling higher-energy ones
• isotopes are atoms of the same element that have the same number of protons but different number of neutrons
• primary standard is a substance which can be obtained in a stable, pure and soluble form so it can be weighed out
• cathode rays are negiatively charged particles that are emitted from the cathode
• paulines exclusion principle is that no more that 2 electrons may occupy an orbital and they must have opposite spin
• electronegativity is the relative attraction that an atom in a molecule had for the shared pair of electrons in a covanlent bond
• atomic radius is half the distance between the nuclei of 2 atoms of the same element that are joined together by a single covalent bond
• hunds rule if maximum multiplicity is 2 or more orbitals of equal energy are available the electrons may occupy then singly before filling them in pairs
• electron configuration is the arranent of electons in an atom of an element
• newlands octaves the arrangement of elements in which the first and eighth element continuing from a particular element have similar properties
• radioactivity spontaneous breaking up of unstable nuclear with the emission of one or more types of radiation