3.1.1 Periodicity

• • Elements are arranged in order of increasing atomic number in the periodic table.
• • Period - the horizontal rows in the periodic table
• • Group - the vertical columns
• • Periodicity - the repeating trends in chemical & physical properties
• What change happened across each period?

  • Elements change from metals to non-metals
• How can electron configuration be written in short?

  • The noble gas before the element is used to abbreviate
• Define first ionisation energy:

  • The energy required to remove one electron from each atom in on mole of the gaseous element to form one mole of gaseous 1+ ions
• Write first ionisation energy for magnesium:

  • Mg (g) —> Mg+ (g) + e-
• What are factors that affect ionisation energy?

  • Atomic radius
  • Nuclear charge
  • Electron shielding or screening
• Explain the trend on this graph:

  • First ionisation energy access period 3 b/c:

  - Increased nuclear charge

  - Decreased atomic radius

  - Same electron shielding

  which means more energy is needed to remove the first electron

  • Dips at Al b/c: outer electron is in a 3p orbital, higher energy than 3s orbital —> less energy needed to remove electron
  • Dips at S b/c: one 3p orbital contains two electrons —> repulsion between paired electrons -> less energy needed to remove one

  
• Why does first ionisation energetic decrease between group 2 to 3?

  • Because in group 3 the outermost electrons are in p orbitals whereas in group 2 they are in s orbital, so the electrons are easier to be removed
• Why does first ionisation energy decrease between group 5 to 6?

  • Group 5 electrons in p orbital are single electrons and in group 6 the outermost electrons are spin paired , with some repulsion. Therefore the electrons are slightly easer to remove.
• Does first ionisation energy increase or decrease between the end of one period and the start of next? Why?

  Decrease:

  • there is increase in atomic radius
  • increase in electron shielding
• Why does first ionisation energy decrease down a group?

  • Shielding increases —> weaker attraction
  • Atomic radius increases —> between the outer electrons & nucleus increases —> weaker attraction
  • Increase in number of protons is outweighted by increase in distance & shielding
• Properties of giant metallic lattices:

  • high melting point
  • Good electrical conductors
  • malleability
  • ductility
• What is a ductile metal?

  • a metal that can be stretched
• What is a malleable metal?

  • a metal can be shaped into different
• Describe the structure, forces boning in every element across period 2:

  • Li & Be: giant metallic, strong attraction between positive ions & negative electrons, metallic bonding
  • B & C : giant covalent, strong forces between atoms; covalent
  • N2, O2, F2, Ne: simple molecular, weak intermolecular forces between molecules, covalent bonding
• Describe the structure, forces & bonding in every elemetn across period 3:

  • Na, Mg, Al : giant metallic , strong attraction between +I’ve ions & electrons,
  • Si : giant covalent, strong forced between atoms
  • P4, S8, Cl2, Ar : simple molecular, weak intermolecular forces, covalent bonding