Atoms Elements and compounds

• the word pure is used in chemistry to describe a substance that consists of only one element or compound
• group 0 contains non-metal elements called noble gases
• compared to other elements noble gases are inert ( extremely unreactive)
• all noble gases have full outer shells
• going down group 0 the atoms become larger and the intermolecular forces between atoms become stronger
• noble gases all have low boiling points
• group 1 contains alkali metals
• alakali metals are soft have relatively low melting points and all have low densities
• atoms of group one elements all have one electron in their outer shell
• going down group one atoms become larger, the outer electron is further from nucleus, and the outer electron is lost more easily
• properties of a typical metal are?

  good conductor of electricity

  good conductor of heat

  shiny

  high density

  malleable

  ductile

  high melting/boiling points
• properties of typical non-metals?

  dull

  low density

  brittle

  low melting/boiling points

  poor conductor of heat

  poor conductor of electricity
• protons have a relative mass of 1
• protons have a relative charge of +1
• neutrons have a relative mass of 1
• neutrons have a relative charge of 0
• electrons relative mass is very small
• electrons relative charge is -1
• isotopes are atoms of the same element with different numbers of neutrons