Calculating Relative Atomic Mass

• What is the structure of an atom?

  An atom consists of a nucleus containing protons and neutrons, surrounded by electrons in shells.
• How can the number of subatomic particles in an atom be calculated?

  The number of subatomic particles can be calculated from the atom's atomic number and mass number.
• What is relative atomic mass?

  • The mean relative mass of the atoms of the different isotopes in an element.
  • It is the number of times heavier an atom is than one-twelfth of a carbon-12 atom.
• What is the standard atom used for comparing the masses of other atoms?

  The carbon-12 atom, \(_{6}^{12}\textrm{C}\), is the standard atom for comparison.
• How is the relative atomic mass of an element calculated?

  The relative atomic mass is calculated from the mass numbers of its isotopes and their abundance.
• What are the two isotopes of chlorine mentioned?

  The two isotopes of chlorine are \(_{17}^{35}\textrm{Cl}\) (chlorine-35) and \(_{17}^{37}\textrm{Cl}\) (chlorine-37).
• What is the abundance of chlorine-35 and chlorine-37?

  The abundance of chlorine-35 is 75% and chlorine-37 is 25%.
• How do you calculate the relative atomic mass of chlorine?

  Use the formula \(A_{r} = \frac{(75 \times 35)+(25 \times 37)}{(75+25)}\).
• What are the mass numbers and abundances of the naturally occurring copper isotopes?

  The mass numbers are 63 with 69% abundance and 65 with 31% abundance.
• What is the relative atomic mass of chlorine calculated to 1 decimal place?

  The relative atomic mass of chlorine is \(35.5\).
• How do you calculate the relative atomic mass of copper?

  Use the formula \(A_{r} = \frac{(69 \times 63)+(31 \times 65)}{(69+31)}\).
• What is the relative atomic mass of copper calculated to 1 decimal place?

  The relative atomic mass of copper is \(63.6\).
• What is the process for calculating relative atomic mass?

  1. Identify the mass numbers and abundances of isotopes.
  2. Use the formula:

  \[

  A_{r} = \frac{(abundance_1 \times mass_1) + (abundance_2 \times mass_2)}{(abundance_1 + abundance_2)}

  \]

  1. Round to the desired decimal place.