topic 1

• Atom


  The smallest part of an element that can exist
• Element


  A substance made of one type of atom only
• Chemical symbol


  • Consists of one or two letters
  • Always starts with a capital letter, with any other letter in lower case
• Chemical symbols


  • O (oxygen)
  • Na (sodium)
• There are over 100 different elements
• The names and symbols of the elements are shown in the periodic table
• Periodic table


  • Elements are arranged into groups with similar properties
  • Groups are numbered from 1 to 7, then 0
  • Metals are on the left of the stepped line, and non-metals are on the right