Unit 4 - Atoms

• Explain why the electrons in the charge cloud cannot escape from the atom?

  because inside the nucleus has positive charge, so it attracts the negative charge (electrons)
• Describe two ways an atom of sodium is different from a atom of lithium?

  1. different no. electrons + protons
  2. Na has 3 electron shells while lithium has 2
• Explain why the mass number is always bigger than the atomic no.?

  mass number includes both number of protons and neutrons while the atomic number includes only the number of protons
• Describe in terms of electrons, how a sodium ion is made from a sodium atom?

  when sodium atom loses an electron (it becomes positivly charged)
• List down the first 3 noble gases and their uses?

  Helium (He) - for flooting balloons

  Neon (Ne) - glows when electricity pass through

  Argon (Ar) - use in light bulb to prevent filament from burning inside it