The Periodic Table

• Group 7:

  • Halogens
  • Similar reactions - 7 electrons on outer shell
  • Non-metals
  • Form white solids in compounds
  • Molecules made of pairs of atoms
• Trends in Group 7:

  • Less reactive down the group
  • Atoms are bigger so the outermost electrons are farther from the nucleus
  • Weaker attraction between electrons and nucleus
  • Harder to gain an electron on the outermost shell
  • Boiling point increases down the group
• Elements in the periodic table are arranged in order of atomic number, meaning that elements with similar properties are in the same groups. It is called a periodic table because similar properties occur at regular intervals.
• • A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
  • Chlorine + Potassium Iodide = Potassium Chloride + Iodine
• Elements in the same group have the same number of electrons in their outermost shell and so they have similar properties e.g. Group 1 have 1 electron on their outer shells.
• Every element in the same period has the same number of shells e.g. all elements in period 3 have 3 shells.
• Metals form positive ions and are found on the left side of the periodic table and towards the bottom.
• Non metals form negative ions and are found on the right side towards the top.
• Group 0:

  • Noble Gases
  • Unreactive
  • Atoms have stable arrangements
  • Full outer shells
  • Boiling point increases down the group
  • Gases become more dense down the group
• The elements in the periodic table are arranged in order of atomic (proton) number and so that elements with similar properties are in columns, known as groups. The table is called a periodic table because similar properties occur at regular intervals.
• Elements in the same group in the periodic table have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties.v
• Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of their atomic weights.
• The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed.
• Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights.
• Elements with properties predicted by Mendeleev were discovered and filled the gaps. Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.
• Elements that react to form positive ions are metals.
• Elements that do not form positive ions are non-metals.
• The majority of elements are metals. Metals are found to the left and towards the bottom of the periodic table. Non-metals are found towards the right and top of the periodic table.
• Metals are located on the left side of the periodic table.
• Non-metals are located on the right side of the periodic table.
• Group 1:

  • alkali metals
  • 1 electron on outer shell
  • reactivity increases down the group
• Group 1:

  • metal + oxygen ---> metal oxide
  • metal + chlorine ---> metal chloride
  • alkali metal + water ---> metal hydroxide + hydrogen
• A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
• Displacement is a chemical reaction in which a more reactive element displaces a less reactive element from a compound and takes its place.
• Fluorine is a pale yellow gas at room temperature.
• Chlorine is a green gas at room temperature.
• Bromine is an orange liquid at room temperature.
• Iodine as a grey solid forms a purple vapour when warmed. It is brown when a liquid.
• • atoms become bigger​ down the group
  • more electron shells
  • outermost electrons further from nucleus
  • weaker attraction between electrons and nucleus
  • more easily lost due to weaker attraction
  • reactivity down group increases
• • atoms become bigger​ down the group
  • more electron shells
  • outermost electrons further from nucleus
  • weaker attraction between electrons and nucleus
  • harder to gain due to weaker attraction
  • reactivity down group decreases