Physical properties of period 3 elements

• Along period 3, the atomic radius decreases because there's an increase in nuclear charge but the same amount of shielding so the electron shells are held closer to the nucleus
• Along period 3, electronegativity increases as there is an increase in nuclear charge so the elements have the greater ability to attract a pair of electrons in a covalent bond
• Across period 3, the general trend is that ionisation energy increases due to increase in nuclear charge so the electrons are more closer to the nucleus and more energy is required to remove it .
• There's two outliers in ionisation

  • Al has a lower ionisation energy then Mg because Mg is having it's 3s electron removed while Al is having it's 3p electron removed which is higher in energy and further away from nucleus so less energy is needed to remove electron
  • Sulfur has a lower ionisation energy then P because it has paired electron in it's 3p orbital so they would repel from each other and so less energy needed to remove it
• The melting/boiling point increases from Na to Al because

  • The charge of the metal ion increases
  • The size of the metal ion decreases
  • So there's a stronger metallic bond
• Silicon has the highest melting/boiling point because

  • It has a macromolecular structure
  • With lots of covalent bond which are very strong
• Phosphorus, sulfur and chlorine are simple molecular structure with Van der Waais forces

  • The bigger the molecule , the stronger the Van der Waais forces
  • So Sulfur has a higher melting/boiling point because it's S8 compared to P4 and Cl2
  • Argon is monoatomic so it's the weakest
• Aluminium has the highest boiling point because

  • As silicon has been melted most of it's strong covalent bonds have been broken so boiling it requires only a small amount of energy
  • In liquid state Aluminium still has strong electrostatic attraction between ions and delocalised electrons so a large amount of energy is required to boil