chemistry

• element


  A pure substance made of only one kind of atom

  
• atom


  the smallest component of an element having the chemical properties of the element

  
• periodic table


  a table of the chemical elements arranged in order of atomic number, usually in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in vertical columns.

  
• compound


  A substance made up of atoms of two or more different elements joined by chemical bonds

  
• electron


  A tiny, negatively charged particle that moves around the nucleus of an atom.

  
• nucleus


  A region that is located at the centre of an atom and contains most of the atom's mass (protons and neutrons)
• proton


  A subatomic particle that has a positive charge and that is found in the nucleus of an atom

  
• neutron


  A subatomic particle that has no charge and that is found in the nucleus of an atom

  
• atomic number


  The number of protons in the nucleus of an atom

  
• atomic mass


  The average mass of all the isotopes of an element

  
• mixture


  A combination of two or more substances that arenotchemically combined

  
• chemical reaction


  the process by which one or more substances change to produce one or more different substances

  
• mass


  A measure of the amount of matter in an object

  
• (g)


  indicates that a substance in a chemical equation is a gas
• (s)


  indicates that a substance in a chemical equation is a solid
• (aq)


  indicates that a substance in a chemical equation is dissolved in solution
• (l)


  indicates that a substance in a chemical equation is a liquid
• chemical formula


  A combination of chemical symbols and numbers to represent a substance

  
• chemical equation


  A representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products

  
• chromatography


  A technique that is used to separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material.

  
• filtration


  A process that separates materials based on the size of their particles.

  
• distillation


  A process used to separate dissolved solids from a liquid, which is boiled to produce a vapor that is then condensed into a liquid

  
• crystallization


  A separation technique that produces pure solid particles of a substance from a solution that contains the dissolved substance.

  
• leibig condenser


  Glassware used to condense water vapour, that consists of two tubes one inside the other with space between for circulation of water.

  
• fractional distillation


  The separation of the components in a mixture of liquids having different boiling points by vaporization.

  
• John Dalton


  English chemist who developed the Atomic theory of matter through an experiment of gases. His theory states: A) All elements are composed of atoms and atoms can't be divided or destroyed. B) Atoms of the same element are exactly alike. C) Atoms of different elements are different from each other. D) The atoms of 2 or more elements can join together to form types of matter called compounds.

  
• J. J. Thompson


  Proposed the "plum pudding" model of the atom, with electrons as negative particles embedded in a positive cloud.

  
• plum-pudding model


  negatively charged electrons were small particles held within a positively charged sphere, proposed by Thompson

  
• Ernest Rutherford


  British physicist (born in New Zealand) who discovered the atomic nucleus and proposed a nuclear model of the atom (1871-1937)

  
• Niels Bohr


  Discovered electrons travel around the nucleus in well-defined energy levels. Electrons that absorb energy move to a higher energy level. Electrons that give off light energy return to their normal ground state or energy level.

  
• James Chadwick


  A British physicist, who confirmed the existence ofneutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons in the electron cloud model.

  
• ion


  A particle that is electrically charged (positive or negative)
• isotope


  Atoms of the same element that have different numbers of neutrons

  
• mass number


  the sum of the number of neutrons and protons in an atomic nucleus
• number of neutrons


  mass number - atomic number
• charge of proton


  +1

  
• charge of neutron


  0

  
• charge of electron


  -1

  
• electron shells


  An energy level representing the distance of an electron from the nucleus of an atom.

  
• electronic structure


  The arrangement of electrons in an atom or molecule.