PERIODICITY

• Definition of Covalent Radius

  Half the distance between the nuclei of two bonded atoms
• Why do group 8 elements not have a covalent radius?

  Group 8 elements do not form bonds with other atoms.
• Covalent Radius across a period?

  As you go across a period, atomic number decreases because of increased nuclear charge which causes electrons to be pulled closer to the nucleus.
• Covalent radius down a group.

  Atomic size increases because of increased energy levels, causing outer electrons to be further from the positive nucleus and shielded by inner electrons.
• Definition of Ionisation Energy?

  Energy required to remove one mole of electron from one mole of atoms in a gaseous state.
• Ionisation Energy across a period?

  Ionisation energy increases because nuclear charge increases, making it more difficult to remove electrons from the atom.
• Ionisation Energy going down a group,

  Ionisation Energy decreases because of increased energy levels, outer electrons are further from nucleus and shielded by inner electrons
• Definition of Electronegativity?


  Measure of attraction an atom has for the electrons in a bond.
• Electronegativity going across a period?

  Electronegativity increases because nuclear charge increases.
• Electronegativity going down a group?

  Electronegativity decreases because of increased energy levels, outer electrons further from nucleus and shielded by inner electrons.