Non-metals included on the Periodic Table based on the IOUPAC 1985 standard
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What are Non-metals? Define Non-metals
Non-metals are used as a term in Periodic Chemistry when classifying the chemical elements. Each element can usually be classified as a metal or a non-metal based on their general Physical and Chemical Properties. Non-metals  are any of the non-metallic elements within Groups 14,15 and 16 in the Periodic Table (see the List of Non-metals). Non-metallic elements exist, at room temperature, in two of the three States of Matter: Gases (such as oxygen) and Solids (such as carbon).
What are Non-metals? What elements are classified as Non-metals?
There is a great deal of variation among this group of 7 elements classified as Non-Metals. Three of the elements are gases and four are solids at normal room temperature. The Non-metals that are are gases are Hydrogen, Nitrogen and Oxygen. The Non-metals that are are solids are Carbon, Phosphorus, Selenium and Sulfer. The properties of non-metals are therefore not universal or as consistent as the metals.

What are Non-metals? Common Properties of Solid Non-metals
Elements described as the solid Non-metals have low melting points compared to the metals. They are poor conductors of heat and electricity, they are brittle solids, not ductile in their solid state – they cannot be rolled into wires or pounded into sheets. They are usually dull and therefore show no metallic luster and they do not reflect light. They also have a low density.

Common properties of Solid Non-metals
The elements classed as solid Non-metals therefore have some of the following properties in common:

  • Poor thermal conductors
  • Poor electrical conductors
  • Low Density
  • Dull, Brittle solids
  • Little or no metallic luster
  • High ionization energies
  • High electro-negativities

Non-metals List – Chemical Elements in the Periodic Table
The elements contained in the classification of Non-metals list are as follows:

  • Hydrogen – a gas
  • Carbon a solid
  • Nitrogen a gas
  • Oxygen a gas
  • Phosphorus a solid
  • Sulfur a solid
  • Seleniuma solid