Period 3

• Atomic radius decreases across a period
• Mg is smaller than Na because there are more prisons attracting the electrons towards the nucleus
• first ionisation energy generally increases across a period
• ionisation energy decreases between Mg and Al ad between P and S
• there is a dip between group 2 and group 3 as electrons start to fill the p sub shell
• there is a dip between group 5 and group 6 as pairs of electrons start to fill the same p orbitals
• across period 3 shielding stays roughly the same
• Si is a giant covalent lattice
• going across period 3 metals melting point increases
• melting point increases across period 3 metals because he metal cations each have a higher charge they therefore have more delocalised electros. this means that there is more attraction between each cation and the delocalised electrons
• one silicon atom can bond with any number of other silicon atoms
• 4 phosphorous atoms can bond together
• 8 sulfur atoms can bond together
• a molecule which is very large can also be called a macromolecule
• the period 3 non metals melting points are:

  Si>S>P>Cl>Ar
• only Na, Mg and Cl react with cold or room-temperature water
• sodium + cold water undergoes a redox reaction
• Magnesium + cold water undergoes a redox reaction
• Magnesium + stem undergoes a redox reaction
• 2Na(s) + 2H2O (l)—> 2NaOH(aq) + H2(g)
• Mg(s) +2H2O(l) —> Mg(OH)2(aq) +H2(g)
• Mg(s) +H2O(g) —> MgO(s) +H2(g)
• Sodium + Oxygen:

  sodium burns with a yellow flame

  sodium is oxidised

  Na2O and Na2O2 is formed
• Magnesium + Oxygen:

  Magnesium burns with a white flame

  Magnesium is oxidised

  MgO is formed
• Aluminium + Oxygen —> Al2O3
• Silicon + Oxygen —> SiO2
• both silicon and aluminium burn with a white flame in O2
• the highest oxide of phosphorous is P4O10
• when oxygen is in short supply Phosphorous forms P4O6
• the highest oxide of sulfur is SO3
• the most common oxide of sulfur is SO2
• P burns with a white flame and produce a white smoke
• Sulfur burns in oxygen with a blue flame
• Na2O is an ionic lattice , strong electrostatic attraction so high melting point. Similarly with Mg and Al
• SiO2 strong covalent bonds, high melting point
• P4O10 has a simple covalent structure with a low melting point
• SO3 and SO2 are both simple covalent structures, SO3 is smaller so has a higher melting point than SO2. SO3 is liquid at room temperature, SO2 is gaseous as room temperature
• Al2O3‘s bonding has some covalent character
• Al2O3 has some covalent character because the Al has a higher nuclear charge, so atomic radius is smaller. therefore the cations are closer to the oxygen anions
• SiO2 and Al2O3 are not soluble in water