2.1.1 & 2.1.2

• What does the atomic number, Z, represent in an atom?

  The number of protons in the nucleus
• What is the mass number, A, of an atom?

  The total number of protons and neutrons in the atom
• How do you calculate the number of neutrons in an atom?

  Number of neutrons = A - Z
• What are isotopes?

  • Atoms of the same element
  • Same number of protons
  • Different numbers of neutrons
  • Similar chemical properties
  • Slightly varying physical properties due to different masses
• What is the definition of relative isotopic mass?

  The mass of one isotope compared to one twelfth of the mass of one atom of carbon-12
• What is the definition of relative atomic mass?

  The weighted mean mass of one atom compared to one twelfth of the mass of one atom of carbon-12
• What is the definition of relative molecular mass?

  The average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12
• How is relative atomic mass (R.A.M) calculated?

  1. A.M = Σ (isotopic mass x % abundance) / 100
• Why do isotopes of an element have similar chemical properties?

  Because they have the same electronic structure
• If an atom has a mass number of 12 and an atomic number of 6, how many neutrons does it have?

  6 neutrons
• What is the significance of carbon-12 in defining relative masses?

  It serves as the standard for comparing isotopic and atomic masses