The Periodic Table And Energy

• Periodicity is the pattern in physical and chemical properties of elements in the periodic table.
• S block elements are group 1, 2 and Helium.
• N2, O2, F2, Ne, P4, S8, Cl2 and Ar form simple molecular structures held together by weak london forces.
• B, C and Si form giant covalent structures with high melting points because of strong covalent bonds.
• Metals form giant metallic structures with strong electrostatic forces between metal ions and delocalised electrons.
• Across a Period, Number of protons increases so there is a larger nuclear pull but electron shielding remains constant so outer electrons become closer to the nucleus and atomic radius decreases.
• Down a group, the number of protons increases so nuclear pull increases, but electron shielding increases with the amount of energy levels so valence electrons are repelled and atomic radius increases.
• Down a group, ionisation energy decreases.
• Traversing a period, first ionisation energy increases.
• Traversing a period there are small decreases in first ionisation energy because of sub shells being half or completely full.
• D block elements are the transition metals.
• F block elements are the lanthanoids and the actinoids
• P block elements are groups 13-18 excluding helium.
• The halogens are diatomic, non-polar molecules that consist of a single covalent molecule and react to form -1 anions.
• Halogens are powerful oxidising agents and have seven valence electrons.
• The Boiling point of the halogens increases down the group as the number of shells is increasing so there a more electrons allowing for greater london forces between molecules.
• Fluorine and Chlorine are gases at room temperature.
• Bromine is a liquid at room temperature
• Iodine is a solid at room temperature.
• Chlorine is often used in water treatment as it reacts with water to form solutions which kill bacteria. But there are concerns with it forming chlorinated hydrocarbons.
• Cl2 + H2O > HCl + HClO
• Cl2 + 2NaOH > NaCl + NaClO + H2O
• Disproportionation reactions are when a single species is both oxidised and reduced.
• If you add acidified silver nitrate to a solution containing halide ions, an insoluble silver salt precipitate will form.
• Chloride forms a white precipitate, Bromide forms a cream precipitate, Iodide forms a yellow precipitate.
• Chloride precipitate would dissolve in dilute ammonia. Bromide precipitate would dissolve in concentrated ammonia. Iodide precipitate wouldn't dissolve in any form of ammonia.
• To Test for carbonate ions, we would add HNO3 and bubble solution through limewater. If carbonate ions are present, we would see effervescence. 
• To Test for sulfate ions, you would add a solution containing Ba2+ ions (e.g. Barium Nitrate). If present, barium sulfate would form which is a white precipitate.
• It is important to carry out the carbonate test before the sulfate, as barium carbonate is also a white precipitate.
• Moving down group 2, the alkalinity of the metal hydroxide formed increases, meaning the pH increases and they become more alkaline.
• caium Hydroxide is used to neutralise acidic soils.
• Magnesium hydroxide and calcium carbonate are used as antacids to neutralise stomach acid.
• Helium is the element with the highest first ionisation energy
• Sulfur forms a compound with chlorine that has an octahedral shape.
• At room temperature and pressure, oxygen has a density of 1.33 x 10^ -3