Definitions

• Chemistry


  The study of matter
• Fundamental concepts


  • The Atom
  • Element
  • Atom
• Element


  • A substance which cannot be broken down into a simpler substance by chemical means
• Atom


  The smallest part of an element
• Dalton's atomic theory


  • All matter is made up of very small particles called atoms
  • All atoms are indivisible. They cannot be broken down into simpler particles
  • Atoms cannot be created or destroyed
• Cathode rays


  A beam of electrons (negative charge) emitted from the cathode of a high-vacuum tube
• Plum-pudding model


  Where the atom where negative electrons were embedded in a sphere of positive charge (Thomson)
• Alpha particles


  The nuclei of Helium atoms produced by certain radioactive substances, positively charged
• Continuous spectrum of light


  Contains all possible wavelengths of light i.e. all the colours of the rainbow
• Emission line spectrum of light

  Energy is concentrated at particular wavelengths, i.e. coloured lines on a black background
• Energy Level


  The fixed/ definite amount of energy which an electron can have in an atom
• Ground state of an electron

  When an electron is in the lowest energy level available to it
• Ground state of an atom


  When all the electrons in an atom are in the lowest energy levels available to them
• Excited electron


  An electron which has absorbed energy (from heat, electricity etc.) and has moved up to a higher level. This state is unstable and temporary
• Wave-particle duality


  Electrons have some properties of particles and some properties of waves (De Broglie)
• Sublevel


  A division of a main energy level and consists of one or more orbitals of the same energy
• Heisenberg's Uncertainty Principle


  It is impossible to measure at the same time both the velocity and the position of an electron
• Orbit


  The fixed path one body takes around another
• Orbital


  A region in space within which there is a high probability of finding an electron
• Aufbau Principle


  When building up the electron configuration of an atom the electrons always occupy the lowest energy level available to them
• Hund's Rule of Maximum Multiplicity

  When 2 or more orbitals of equal energy are available, the electrons fill them singly before filling them in pairs
• Pauli's Exclusion Principle


  No more than 2 electrons may occupy an orbital and they must have opposite magnetic spin
• Atomic number


  The number of protons in the nucleus of the atom. Determines the identity of the element
• Atomic mass number


  The number of protons and neutrons in the nucleus of an atom of that element
• Gas


  A substance that has no well-defined boundaries but diffuses rapidly to fill any container in which it is placed
• Diffusion


  The movement of particles from an area of high concentration to an area of low concentration
• Brownian movement


  The constant, random, straight line movement of gas particles
• Boyle's Law


  States that at constant temperature, the volume of a fixed mass of gas is inversely equal proportional to its pressure. P1V1 = P2V2
• Inversely proportional


  As one increases the other decreases
• Charles' Law


  States that for a fixed mass of gas of constant pressure, the volume is directly proportional to the temperature. i.e. as temperature increases, volume also increases
• General Gas Law/ Combined Gas Law

  P1V1/T1 = P2V2/T2
• Gay-Lussac's Law of Combining Volumes

  In a reaction between gases, the volumes of the reacting gases and the volumes of any gaseous products are in the ratio of small whole numbers provided the volumes are measured at the same temperature and pressure
• Avogadro's Law


  Equal volumes of gases contain equal numbers of particles under the same conditions of temperature and pressure
• Ideal Gas


  A gas which obeys all the assumptions of the kinetic theory of gases under all such conditions of temperature and pressure. No such gas exists. Most gases do behave as ideal under most conditions of temperature and pressure
• Real gases


  Differ from ideal gases because (i) forces of attraction and repulsion do exist between the molecules and (ii) the volume of the molecules is not negligible
• Ideal Gas Equation


  PV = nRT
• Triad


  A group of 3 elements where the atomic weight (mass) of the middle elements is approx. equal to the average of the other two elements
• Newlands octaves


  Arrangements of elements in which the 1st and the 8th element, counting from a particular element have similar properties
• The modern periodic table

  An arrangement of elements in order of increasing atomic number
• Mendeleev's periodic law


  He noticed that the properties of the elements repeated periodically. Arranged them in order of increasing atomic weight