Science Term 2

• Atoms are the particles that make up all the substances in the universe
• Indirect evidence


  Evidence that doesn't involve direct observation of the particles
• Neutrons are slightly heavier than protons
• Neutrons are 1800 times heavier than electrons
• Almost all of an atom's mass is in its nucleus
• Protons


  Carry a positive charged ion
• Neutrons


  Carry a neutral charge
• Electrons


  Are negatively charged
• Atoms are electrically neutral because the number of electrons is always the same as the number of protons
• Elements


  The building blocks from which all substances are made
• Chemical formula


  Tells you what elements make up a compound and in what proportions
• Atomic number


  The number of protons in the nucleus of an atom
• Alkali metals


  • Form +1 ions
  • Are far too reactive to be found naturally in their pure forms
  • Have typically metallic properties
  • Display similar extreme chemical behaviors
• Group 2 elements


  Alkaline earths
• Group 14


  Display a wide range of properties
• Pure carbon


  • Exists in many forms of allotropes, the most common being amorphous carbon, graphite, diamond and buckyballs
• Organic molecules


  Make up all the living things, fossil fuels and polymers
• Halogens


  • Form -1 ions
  • Are not found in nature in their pure forms
  • Get bigger and less reactive down the group
  • All form molecules that are made with 2 atoms
  • Have coloured and poisonous gasses
• Group 18


  Noble gasses
• Atomic number


  Number of protons in an atom
• Atoms


  The particles that make up all the materials; the smallest parts of an element that can take part in a chemical reaction
• Elements


  Substances composed of atoms with the same atomic number
• Indirect evidence


  Evidence that does not involve direct observation of particles
• Isotopes


  Atoms of the same element with different numbered neutrons
• Nucleus


  Heavy core at the center of the atom
• Groups


  Vertical columns of the periodic table
• Lanthanides


  A special block of metallic elements with atomic numbers
• Alkali metals


  Group 1 elements
• Alkaline earths


  Group 2 elements
• Allotropes


  Forms of the same element that have different molecular structure and therefore different properties
• Halogens


  Group 17 elements
• Noble gasses


  Group 18 elements
• Organic


  Compound that is or was part of a living thing; contains carbon
• Organic molecule


  Molecules that have skeletons of carbon atoms
• Electron configuration


  Arrangements of electrons in electron shells
• Electron shells


  Also known as energy levels, the regions surrounding the nucleus where electrons may be found
• Ground state


  The lowest energy arrangement of an atom's electrons in energy levels (shells)