Chem

• What is the definition of covalent radius?

  Half the distance between two bonded nuclei
• Why does the covalent radius increase down a group?

  More filled electron shells increase shielding
• Why does the covalent radius decrease across a period?

  More protons attract outer electrons more strongly
• What is ionisation energy?

  Energy to remove one mole of electrons
• Why does ionisation energy decrease down a group?

  Increased shielding weakens nucleus attraction
• Why does ionisation energy increase across a period?

  More protons strengthen attraction for outer electrons
• What is electronegativity?

  Attraction for shared pair of electrons
• Why does electronegativity decrease down a group?

  Increased shielding weakens attraction for shared electrons
• Why does electronegativity increase across a period?

  More protons strengthen attraction for bonded electrons
• What are the three main trends in the periodic table?

  • Covalent radius
  • Ionisation energy
  • Electronegativity
• How do the trends in covalent radius, ionisation energy, and electronegativity relate to nuclear charge and shielding?

  • Covalent radius increases down due to shielding
  • Ionisation energy decreases down due to shielding
  • Electronegativity decreases down due to shielding
  • All trends increase across due to increased nuclear charge
• How are elements arranged in the periodic table?

  In periods of increasing atomic number
• What can chemists determine from the periodic table?

  Reactivity, properties, and bonding of elements
• What types of bonding occur within the first 20 elements?

  • Metallic bonding
  • Covalent bonding
  • Ionic bonding
• Which elements exhibit metallic bonding?

  Lithium, beryllium, sodium, magnesium
• Why can metallic elements conduct electricity?

  Electrons are loosely held and delocalized
• What is covalent bonding characterized by?

  Attraction between positive nuclei and shared electrons
• What distinguishes polar covalent bonds from non-polar covalent bonds?

  Electrons are shared unequally in polar bonds
• What are London dispersion forces?

  Weak forces of attraction between all atoms and molecules
• What causes London dispersion forces?

  Uneven distribution of electrons causing temporary dipoles
• What are monatomic elements?

  Elements consisting of only one atom
• Why don't monatomic elements form ionic or covalent bonds?

  They have full outer electron shells
• What are the types of intramolecular bonding?

  • Pure covalent bonds
  • Polar covalent bonds
  • Ionic bonds
• What characterizes pure covalent bonds?

  Atoms with the same electronegativity