Elements

• An element is a substance that only contains atoms with the same number of protons.


  What is an element?
• The periodic table shows all known elements, arranged by increasing atomic mass. The elements are grouped into periods (rows) and groups (columns).
• A compound is made up from two or more elements chemically combined together.
• Periodic Table


  A table that organises the 117 known elements
• There are about 100 elements
• Atom


  The smallest unit of an element that retains its chemical properties
• Atomic number


  The number of protons in the nucleus of an atom
• Elements consist of atoms with the same atomic number
• The number of protons in the nucleus decides what type of element it is
• Elements can be represented by symbols
• Element symbols

  • Na-sodium
  • Fe-iron
  • P-phosphorus
• Isotopes

  Atoms of the same element that have the same number of protons but different numbers of neutrons
• Isotopes

  • Carbon-12
  • Carbon-13
• Isotopes have the same atomic number but different mass numbers
• Many elements can exist as a number of different isotopes
• Relative atomic mass

  The average mass of the atoms of an element, taking into account the different masses and abundances of its isotopes
• Calculating relative atomic mass

  1. Sum of (isotope abundance x isotope mass number) for all isotopes

  2. Divide by sum of all isotopes
• The relative atomic mass of copper is 63.5