Elements, Isotopes & Relative Atomic Mass

• Structure of an atom

  Central nucleus comprises protons and neutrons, with electrons orbiting the nucleus
• Number of protons determines the element


  The smallest element is hydrogen with one proton, followed by helium with two protons
• Characteristics of elements

  • Around 100 different elements, organized into the periodic table with each box representing a different element
• Nuclear symbols

  Boxes in the periodic table representing different elements, with the atomic number (number of protons) in the bottom left
• Atomic number


  Unique to each element, representing the number of protons in the atoms of that element
• An atom with a certain number of protons must be that specific element
• Example: Atom with two protons must be helium
• Example: Atom with three protons cannot be carbon, it must be lithium
• Element symbols

  One or two letter symbols representing the element name
• Example: C stands for carbon, Li stands for lithium
• Some symbols may be confusing, e.g., sodium is Na and iron is Fe
• Most periodic tables have both the symbol and the name for clarification
• Number of neutrons in isotopes

  Can vary while the number of protons remains the same
• Isotopes

  Different forms of the same element with the same number of protons but different number of neutrons
• Isotopes react chemically in basically the same way despite having different numbers of neutrons
• Carbon 13 has a mass number of 13 due to having seven neutrons and 6 electrons
• Isotopes


  Vary only in the number of neutrons they have, chemically reacting in basically the same way
• Different isotopes have different masses
• Calculating relative atomic mass

  Multiply each isotope's abundance by its mass, sum these figures, then divide by the sum of the abundances of all the isotopes
• Stable isotopes of copper

  • Copper 63 (abundance 69.2%)
  • Copper 65 (abundance 30.8%)
• Abundance of isotopes


  Refers to how common or rare an isotope is
• Relative atomic mass is the average mass of all the isotopes that make up a particular element
• Speaker: 'Quote'
• The equation for relative atomic mass is the sum of isotope abundance times isotope mass divided by the sum of the abundances of all the isotopes
• In the case of copper, the relative atomic mass is calculated as 63.6