Atomic Structure

• A more reactive halogen can displace a less reactive halogen in an aqueous solution of its salt.

  e.g. chlorine can displace bromine in a solution of potassium bromide

  Chlorine + Potassium Bromide -> Potassium chloride + bromine
• What is the total number of protons and neutrons in an atom called?

  mass number
• Why does iodine have a higher boiling point than chlorine?

  The forces between iodine molecules are stronger.
• Why does potassium iodide conduct electricity?

  It contains ions which can move.
• Why is chlorine more reactive than iodine?

  Chlorine's outer electrons are closer to the nucleus so chlorine has less shielding and the nucleus has a greater attraction for outer electrons so chlorine gains an electron more easily.
• What is an isotope?

  An atom with the same number of protons but different number of neutrons.
• Gallium was discovered years after Mendeleev finished his periodic table. Explain why the discovery of gallium proved Mendeleev was correct.

  1. Gallium matched the properties of other group 3 elements.
  2. Mendeleev left a gap for gallium.
• Why do the boiling points of group 0 elements increase as you go down the group?

  The size of the molecules increase so the intermolecular forces increase in strength, more energy is needed to break them.
• Why does the reactivity of group 0 elements decrease as you go down the group?

  The outer shell becomes further away from the nucleus so the nucleus has less attraction for new electrons and there is increased shielding so an electron is gained less easily.
• What increases as you go further down group 7?

  The relative molecular mass

  Melting point

  Boiling point
• What increases as you go further down Group 0?

  The boiling points

  Relative atomic mass
• Elements that lose electrons and form positive ions are metals.

  Elements that gain electrons and form negative ions are non-metals.
• The charge on an ion is usually the same as the element's group number because it shows how many electrons have been lost or gained.
• What is Avogadro's Constant?

  6.02 x 10^23
• Relative atomic mass = (mass number x percentage abundance) + (mass number x percentage abundance) /100
• What are group 7 elements known as ?

  Halogens
• Explain the trend in the melting points of Group 7 elements.

  The molecules increase in size so the intermolecular forces increase so the melting points increase going down the group.