The periodic table

• The mass number = the number of protons + the number of neutrons
• The mass number is 7. This means that the total number of protons and neutrons is 7

  
• The atomic number is 3. This means that there are 3 protons in the nucleus

  
• Number of neutrons = mass number - atomic number
• An atom has no overall charge. This means the number of

  electrons is equal to the number of protons.

  so atomic number = number of electrons

  Atoms of the same element have the same number of protons.
• Mass number = protons + neutrons
• Atomic number = protons
• How can you calculate protons?


  Protons = atomic number
• How can you calculate Electrons?

  Electrons = atomic number
• How can you calculate neutrons?

  Mass number - Atomic number
• In a proton, the relative mass is 1 and the relative charge is +1
• In a Neutron, the relative mass is 1 but the relative charge is 0
• In an electron, the relative charge is -1 and the relative masss is almost 0
• How are the groups arranged in the periodic table?

  According to their properties.
• How can you tell that the alkali metals are very reactive?

  According to their properties.
• How can you tell the noble gases are unreactive?

  Full shell of outer electrons.