Structure of the atom

• Atoms

  • a positively charged nucleus
  • surrounded by negatively charged electrons
  • the radius of the nucleus is much smaller than the radius of the atom
  • the nucleus contains almost all of the mass

  A) nucleus

  B) electron

  
• Subatomic Particles

  • The nuclei of all atoms contain subatomic particles called protons and most also contain neutrons.

  A) electron

  B) proton

  C) neutron

  
• The masses of subatomic particles are very tiny. Instead of writing their actual masses in kilograms, we often use their relative masses. The relative mass of a proton is 1, and a particle with a relative mass smaller than 1 has less mass.

  A) 1

  B) 1

  C) 0

  D) -1

  E) +