relative atomic mass

• What is the size of atoms in centimeters?


  About \(10^{-8}\) centimeters
• How does the size of an atom compare to an apple if every atom in an apple was the size of an apple?

  The apple would be the size of the Earth
• Why is mass given in relative terms?

  To avoid working with very small numbers
• What is the international standard for relative mass comparison?

  The carbon-12 isotope
• What unit is atomic mass measured in?

  The unified atomic mass unit (u)
• What mass is assigned to carbon-12 in unified atomic mass units?

  12 u
• What does 1 u weigh in kilograms?

  Approximately \(1.6605 \times 10^{-27}\) kilograms
• What is the definition of relative isotopic mass?

  The mass of an atom of an isotope compared with \( \frac{1}{12} \) of the mass of an atom of carbon-12
• What is the relative isotopic mass of chlorine with a mass number of 35?

  35
• What is the relative isotopic mass of chlorine with a mass number of 37?

  37
• What is the definition of relative atomic mass?

  The weighted mean mass of an atom of an element compared with \( \frac{1}{12} \) of the mass of an atom of carbon-12
• Why is relative atomic mass useful?

  It accounts for the mixture of isotopes in elements
• How do you calculate the relative atomic mass of chlorine given its isotopes' abundances?

  By multiplying the mass number of each isotope by its percentage abundance and dividing by 100
• What is the relative atomic mass of chlorine if 75.77% is chlorine-35 and 24.23% is chlorine-37?

  35.49
• Why is the mass number of chlorine not a whole number?

  Because it is a weighted average of its isotopes
• What is the relative molecular mass represented by?

  m r
• What is an example of a diatomic molecule?

  Oxygen (O₂)
• What is the relative molecular mass of chlorine gas (Cl₂) if one chlorine atom has a mass number of 35.45?

  70.9
• What is relative formula mass used for?

  To calculate the mass of ionic compounds
• What is the relative formula mass of sodium chloride (NaCl) if sodium has a relative atomic mass of 23 and chlorine has a relative atomic mass of 35.45?

  58.45
• What are the different types of atomic masses and their definitions?

  • Relative isotopic mass: Mass of an isotope compared to \( \frac{1}{12} \) of carbon-12.
  • Relative atomic mass: Weighted mean mass of an atom compared to \( \frac{1}{12} \) of carbon-12.
  • Relative molecular mass: Mass of a molecule compared to \( \frac{1}{12} \) of carbon-12.
  • Relative formula mass: Mass of an ionic compound's formula unit compared to \( \frac{1}{12} \) of carbon-12.
• What is the relative formula mass of trisodium phosphate (Na₃PO₄)?

  160
• How do you calculate the relative atomic mass of rubidium using its isotopes?

  By multiplying each isotope's mass number by its percentage abundance and dividing by 100
• What is the relative atomic mass of rubidium if one isotope has a mass number of 85 and abundance of 72.15% and the other has a mass number of 87 and abundance of 27.85%?

  85.557
• Why is the mass number of magnesium given as 24.31 and not as an integer?

  Because it is the average of the isotopes of magnesium
• What is the significance of relative isotopic mass and relative atomic mass in the periodic table?

  • Relative isotopic mass helps identify individual isotopes.
  • Relative atomic mass provides an average mass for elements with multiple isotopes.
  • Both are essential for understanding atomic structure and behavior.