• Ahli kimia cuba mengembangkan dan membuat generalisasi unsur dengan mengklasifikasikannya mengikut ciri-ciri tertentu.
• Pengelasan akan membolehkan para saintis untuk;
  • Mengelaskan sifat kimia dan fizikal.
  • Ramalkan kedudukan unsur.
  • Kenal pasti dan bandingkan unsur dari kumpulan yang berbeza.
  • Ramalkan sifat kimia dan fizikal.

• Electrical wires made from metal can conduct electricity.
• Metal atoms are arranged closely packed and orderly in the solid state.
• Valence electrons of metal atoms can be donated easily and delocalised although in the solid state.
• Metal ions that are positively charged are formed when valence electrons are delocalised.
• All delocalised valence electrons can move freely between the metal structure and form a sea of electrons.
• Electrostatic attraction force between the sea of electrons and the positively charged metal ions forms the metallic bond.

Electrical conductivity of metals

• When the electrons of metal atoms are delocalised in the sea of electrons, the metal can conduct electricity.

• Electrons that move freely in the metal structure carry the charges from the negative terminal to the positive terminal when electricity is supplied.