key terms

• covalent bond

  a shared pair of electrons between two non-metals
• ion 


  an atom/molecule with an electric charge due to the loss/gain of electrons. positive if formed when an atom loses electrons and a negative ion is formed when an atom gains electrons
• ionic bond

  bond formed between the oppositely charged ions when a metal loses electrons to form a positive ion and a non-metal gains these electrons to form a negatively charged ion
• ionic compound

  chemical compound formed of oppositely charged ions, held together by strong electrostatic forces - metal / non- metal
• metallic bond

  bond present in metals between positive metal ions and negative charged delocalised electrons
• atom 


  all mater is made of atoms, atoms are made of smaller subatomic particles called protons, neutrons and electrons giving an atom its mass number, atomic number and electronic structure
• mass number 


  total number of protons and neutrons in a nucleus
• atomic number 


  the charge number of an atomic nucleus
• soluble 


  a substance is soluble if it dissolves in certain fluids
• insoluble 


  a substance(solid) that will not dissolve in a solvent even after mixing
• allotropes 


  more than one physical form in which an element can exist (same element)
• allotropy 


  when an element can form more than one structure