Size and mass of atoms

• Atoms are extremely small with a radius of about 1 x 10-10 metres
• The radius of the nucleus is about 10 000 times smaller than that of the atom, around 1 x 10-14 m
• Most of the atom is actually empty space, with the mass being concentrated in the nucleus and the electrons orbiting in shells around it.
• • The mass number 
  • The symbol for this number is A

  
• The atomic number has the symbol Z

  
• • To put the size of an atom into perspective, if an atom were magnified to the size of a football stadium, then:
  • The nucleus would be the size of a small pea at the centre of the pitch where kick-off takes place
  • The electrons would be orbiting the pea at the outermost seats of the stadium
  • In between the nucleus and the electrons is nothing but empty space