The Periodic Table and Properties of the elements

The Periodic Table

• The position of an element within the periodic table depends on it's atomic (proton) number and it's electronic arrangement.
• The group number depends on the number of electrons in the outer shell, this leads to similar chemical properties.
• The period number relates to how many shells the atom has.
• Because of this there are distinct Periodic Patterns (periodic laws) i.e. Going across any period from left to right, the elements on the left are metallic but the elements on the right are non-metallic
• The group number is the same as the number of electrons on the outer shell.
• The charge of an ion depends on the number of electrons that are gained or lost to achieve a full outer shell.
• Therefore
  • Group 1, 1 electron in an outer shell, loses 1 electron for an outer shell, charge of ion=1+, Metals
  • Group2, 2 electrons in the outer shell, loses 2 electrons for an outer shell, charge of ion=2+, Metals

• • Group 3, 3 electrons in the outer shell, loses 3 electrons for an outer shell, charge of ion=3+, Metals
  • Group 5, 5 electrons in the outer shell, gains 5 electrons for an outer shell, charge of ion=3-, Non-Metals
  • Group 6, 6 electrons in the outer shell, gains 2 electrons for an outer shell, charge of ion=2-, Non-metals
  • Group 7, 7 lectrons in the outer shel, gains 1 electron for an outer shell, charge of ion=1-, non-metals
• Group 4 elements do not count as they are the Transition Metals, and are both Metallic (bottom), and Non-Metallic (top)
• Group 8 elements have a full outershell.

The Alkali Metals

• All are Metals
  • Lithium (Li)
  • Sodium (Na)
  • Potassium (K)
  • Rubidium (Rb)
  • Caesium (Cs)
  • Francium (Fr; Radioactive)
• When these elements react with other elements, they lose the one electron on their outer shell, this forms a positive ion with 1 positive charge (1+).
  • i.e Na (2.8.1) to Na+ (2.8) + e-
• Lithium is the least reactive whilst Francium is the most reactive, as Francium's outer shell is further away from the nucleus (the atomic radius increases), this creates a stronger shielding effect, making it easier to lose an electron.
• The melting point decreases with larger atomic radius.

• Li,Na and K are less dense then water, therefore they float. All react violently with water giving of Hydrogen gas and dissolve to form Alkaline metal Hydroxide.
  • i.e 2Na + 2H2O to 2NaOH + H
• Metal ions are colourless as a gas and liquid but white as a solid.
• They are fully soluble in water except Lithium which is only partially soluble.
• Oxides
  • React easily with water to form metal Hydroxides
    • Na2O + H2O to 2NaOH
• Hydroxides
  • Strong Bases forming strong alkaline solutions in water, when they neutralise acid they form salts and water.

• Chlorides

  • Colourless salts which dissolve easily in water (sodium chloride, sea salt) to produce neutral solutions
• Nitrates
  • The nitrates of Sodium and Potassium decompose with heating to give the nitrite salt and Oxygen
    • 2NaNO3 to 2NaNO2(s) + O2
  • All the nitrates in Group 1 act the same except Lithium which acts like Group 2 elements.
    • 2LiNO3 to 2LiO(s) + NO2(g) + O2

• Carbonates

  • The carbonates of Sodium and Potassium do not decompse by heating, but are soluble in water.
  • However Lithium carbonate behaves like Group 2 Elements
    • Li2 to Li2O(s) + CO2

• All Metals
  • Berylium (Be)
  • Magnesium (Mg)
  • Calcium (Ca)
  • Strontium (Sr)
  • Barium (Ba)
  • Radium (Ra; Radioactive)
• They occur in rocks and minerals
  • Calcium from Calcium carbonate (chalk, limestone, marble)
  • Magnesium from Magnesium chloride (Dolomite)

• When they react with different elements they lose 2 electrons and are therefore less reactive than Group 1 metals.
  • Mg (2.8.2) to Mg2+ (2.8) + 2e-
• As with Group 1 they are more reactive as you descend down the Group, due to the shielding effect
• The melting point decreases as the group descends.
• All Group 2 metals react with cold water but the magnesium reaction is extremely slow. Hydrogen gas and Alkaline Metal hydroxide is formed.
  • i.e. Ca(s) + 2H2O to Ca(OH)2 + H2
• All are colourless when gas and dissolved in water, but white when solid, (unless combined with a coloured negative ion)