Secondary 1 Chapt 8 notes (atoms and molecules)

• Element

  The basic building blocks of matter
• The variety of elements is due to differences in their simplest units
• Atom


  The simplest unit of an element
• Breaking down a piece of silver

  1. Smaller pieces

  2. Simplest unit of element
• Democritus' ideas about atoms are not without error
• Science is evidence based and open to debate
• Size of an atom

  Very small, cannot be seen by the naked eye
• Structure of an atom

  Made up of 3 subatomic particles: protons, neutrons, electrons

  
• Proton


  • Relative mass = 1
  • Relative charge = +1
  • Found in nucleus

  
• Neutron


  • Relative mass = 1
  • Relative charge = 0
  • Found in nucleus

  
• Electron


  • Relative mass = 1/1840
  • Relative charge = -1
  • Found in shells around nucleus

  
• In all atoms, the number of protons and electrons are always equal
• Atoms are electrically neutral as positive and negative charges are equal
• Neutrons have no charge and do not contribute to the charge of an atom
• Isotopes


  Atoms of the same element with the same number of protons but different number of neutrons
• Mass of an atom is mainly contributed by the mass of the nucleus (total mass of protons and neutrons)
• Proton number


  Number of protons in an atom
• Mass number


  Total number of protons and neutrons in an atom
• Each element has a different proton number
• Elements are arranged in the periodic table in ascending proton number
• Molecule


  Made up of two or more atoms chemically combined
• Representations of elements and compounds

  • Hydrogen atom
  • Hydrogen molecule
  • Water molecule
• Representations of elements and compounds

  • Hydrogen
  • Nitrogen
  • Water
  • Carbon dioxide
  • Nitrogen dioxide
• Application of atomic technologies can bring both benefits and issues to mankind
• Human abuse of atomic knowledge or accidents with beneficial applications can cause problems
• Chapters


  • Model of matter
  • atoms molecules
• Atoms


  • nucleus
  • neutrons
  • electrons
  • cook
  • B
  • protons
• Neutrons


  Found in the nucleus, relative mass 1, relative charge 0
• Electrons


  Found in shells surrounding nucleus, relative mass 1/1840, relative charge -1
• Protons


  Found in the nucleus, relative mass 1, relative charge +1
• Protons and electrons are always equal, overall charge is 0</b>
• Neutrons have no charge and do not contribute to the charge of an atom
• The mass of an electron is considered negligible and does not add to the mass of an atom
• The mass of an atom is mainly contributed by the mass of the nucleus, which is the total mass of protons and neutrons
• Molecules


  Made up of two or more atoms chemically combined, may be of the same element or different elements
• Atom of an element


  Only 1 of the same element
• Molecule of an element

  2 or more of the same element
• Molecule of a compound


  More than 1 different element
• If number of protons is more than electrons

  The ion will have a positive charge
• If number of protons is less than electrons

  The ion will have a negative charge