Relative Atomic Mass

• What is meant by relative atomic mass?

  It is the weighted average of the mass numbers of an element's isotopes based on their abundance.
• How is relative atomic mass calculated for an element?

  By taking a weighted average of the mass numbers of its isotopes based on their abundance.
• What are isotopes?

  Isotopes are atoms of the same element with different numbers of neutrons.
• What is the atomic number of chlorine?

  17
• Why do isotopes of chlorine have different mass numbers?

  Because they have different numbers of neutrons.
• How is the relative atomic mass of chlorine determined from its isotopes?

  By taking a weighted average of the mass numbers of its isotopes based on their abundance.
• What is the formula to calculate relative atomic mass based on isotopes?

  Relative atomic mass formula:

  • (mass number of isotope 1 × percent abundance of isotope 1 + mass number of isotope 2 × percent abundance of isotope 2) / 100
• If boron has two isotopes with mass numbers of 10 and 11, how do you calculate its relative atomic mass?

  By applying the formula with the mass numbers 10 and 11 and their abundances of 20% and 80% respectively.
• What is the calculated relative atomic mass of boron?

  10.8
• Why is the relative atomic mass of boron rounded to 11 in the periodic table?

  Because it is rounded up to the nearest whole number for the periodic table.
• How do you calculate the relative atomic mass of magnesium with three isotopes?

  By applying the formula with the mass numbers 24, 25, and 26 and their abundances of 79%, 10%, and 11% respectively.
• What is the calculated relative atomic mass of magnesium?

  24.3
• Why is the relative atomic mass of magnesium rounded down to 24 in the periodic table?

  Because it is rounded down to the nearest whole number for the periodic table.