Atoms and elements of the Periodic Table

• Electrostatic force


  The force holding matter together
• Electromagnetism


  The force combining electrostatic force and magnetism, one of the four forces in our universe
• Like charges


  Repel each other
• Opposite charges


  Attract each other
• Subatomic particles

  • Elementary
  • Composite
• Elementary subatomic particles


  • Quarks
  • Leptons
  • Cannot be divided into other particles
• Composite subatomic particles


  • Protons
  • Neutrons
  • Can be divided into other particles
• Protons


  Positively charged particles deep inside the atom in the nucleus
• Neutrons


  Uncharged particles deep inside the atom in the nucleus
• Types of quarks

  • Up
  • Charm
  • Top
  • Down
  • Strange
  • Bottom
• Protons consist of three quarks: up+2/3+up+2/3+down-1/3
• Neutrons consist of three quarks: up+2/3+down-1/3+down-1/3
• Electrons


  Elementary particle that belongs to leptons, negatively charged particles found in the space around the nucleus, can behave as either particle or wave
• Atomic number (Z)


  The number of protons in the nucleus of an atom
• An atom is neutral and does not have an electrical charge
• Elements are arranged in increasing atomic number
• Mass number (A)


  The mass of the total number of protons and neutrons
• To calculate the number of neutrons in an atom, subtract the number of protons (atomic number)
• Mass number = number of protons + number of neutrons
• The periodic table


  • Horizontal rows are called periods or energy levels
  • Vertical columns are called groups
  • Groups are numbered from 1-18
• Groups in the periodic table

  • Alkali metals (group 1)
  • Alkali earth-metals (group 2)
  • Transition metals (groups 7-12)
  • Halogens (group 17)
  • Noble gases (group 18)
• Valence electrons


  The number of valence electrons is the element's position in that specific period
• Diatomic elements


  • I2
  • Br2
  • Cl2
  • F2
  • O2
  • N2
  • H2