Periodicity

• define periodicity

  repeating trend/pattern
• describe the atomic radius across period 3

  atomic radius decreases

  increased nuclear charge because there is an increased number of protons

  so there is a stronger electrostatic forces of attraction between outer electrons and nucleus

  and similar shielding
• describe the trend in melting points in Na, Mg, Al

  they have metallic bonding

  general increase in melting points as there is an increasing positive charge, more delocalised electrons, so smaller atomic radius

  more energy required to break bonds
• describe the trend in melting points in silicon

  has the highest melting point in period 3

  has a giant covalent structure

  there is lots of strong covalent bonds - lots of energy needed to overcome the strongbonds
• describe the melting point in phosphorous and sunfurl

  phosphorous P4:

  has a simple molecular structure and has weak van der waals forces

  sulfur S8:

  higher melting point than P4 due to a larger simple molecular structure, so has more van der waals forces and so higher melting point
• describe the melting point of chlorine and argon

  chlorine:

  lower melting point than P4 and S8 due to a smaller simple molecular structure and so smaller van der waals

  argon:

  has the lowest melting point because it exists individually, has the weakest van der waals forces
• define ionisation energy

  The minimum amount of energy required to remove one mole of electrons from one mole of atoms in the gaseous state

  Endothermic reaction
• what are the 3 factors affecting ionisation energy?

  shielding

  nuclear charge

  atomic radius
• describe how shielding affects ionisation energy

  The more electron shells, the less energy required because the electrostatic forces of attraction are weaker
• describe how nuclear charge affects ionisation energy

  the more protons in the nucleus, the stronger the electrostatic forces of attraction, so more energy required

  as long as shielding remains simillar
• describe how atomic radius affects the ionisation energy

  the bigger the atom, the smaller the electrostatic forces of attractions, so less energy needed to remove an electron
• describe the general trend in successive ionisation energy

  general increase in energy, because we are removing an electron from an increasingly positive ion

  There’s a jump between magnesium and aluminium in energy as removing electrons from a shell closer to the nucleus

  
• describe the first ionisation energy trends down a group

  decreases down a group

  atomic radius increases going down the group, so the outer electrons are further from the nucleus

  so the electrostatic attraction is weaker

  energy required to remove an electron decreases

  shielding increases going down the group - more shells weaken the forces of attraction, so energy required to remove an electron decreases