Periodicity

• What is a period ?

  • A horizontal row of elements and they show trend in properities as you go across
• what is a group ?

  • a vertical column
  • elements in a group have similar properties and their atoms have the same number of outer shell electrons
• what is periodicity

  • a repeating trend in properties of the elements across each period
• 3 factors that influence or affect the size of the atomic radius

  • 1 ) more shells = a larger atom
  • 2) number of full inner shells as more shells means more shielding , more shielding means weaker attraction between nucleus and outer electrons
  • 3) nuclear charge = number of protons in nucleus , as a higher nuclear charge means more attraction to outer electrons
• atomic radius across a period

  • decreases as you along
  • because shielding stays constant
  • increasing nuclear charge
  • increasing attraction from nucleus
• what is first ionisation energy

  energy needed to convert 1 mole of gaseous atoms into 1 mole of gaseous 1 + ions
• what is the first ionisation energy of magnesium

  • Mg —> Mg+ + e-
• factors which effect the size of the 1st Ie

  • nuclear charge increases ie as pulls the outer electron
  • sheilding decreases ie
  • distance decreases ie as its easier to lose an electron
• trend in IE across a period

  • increases as you go across
  • Because of nuclear charge
  • shielding is constant
  • atomic radius decreases
• What is the 3rd IE of Na

  Na2+ —> Na3+ + e-