periodicity

• What are the groups and periods in the periodic table?

  • Groups: Columns where elements have similar chemical properties due to the same number of outer electrons
  • Periods: Rows ordered by increasing atomic number
• What is the significance of the step line in the periodic table?

  It separates metals on the left from nonmetals on the right
• What are the four main groups of elements in the periodic table mentioned?

  1. Alkali metals (Group 1)
  2. Transition metals (middle section)
  3. Halogens (Group 7)
  4. Noble gases (Group 8)
• How does the bonding change as you move from left to right across the periodic table?

  The bonding changes from metallic to covalent to monatomic
• What is metallic bonding?

  • Defined as an electrostatic attraction between positive metal ion cores and a sea of delocalized negative outer electrons
  • Structure: Lattice of metal ions
• What is covalent bonding?

  • Defined as an electrostatic attraction between positive nuclei and shared pairs of negative electrons
  • Structures: Network lattice or discrete molecule
• What is monatomic bonding?

  Bonding involving single atoms
• How are metallic elements represented in the periodic table?

  • Metallic elements are shaded in red
  • Examples: Lithium, Sodium, Potassium, Beryllium, Magnesium, Calcium, Aluminium
• How are covalent networks represented in the periodic table?

  • Covalent networks are shaded in yellow
  • Examples: Carbon (graphite or diamond), Silicon
• How are small covalent molecules represented in the periodic table?

  • Small covalent molecules are shaded in blue
  • Examples: Phosphorus (P₄), Sulfur (S₈), Carbon (C₆₀)
• What is the definition of covalent radius?

  Covalent radius is half the distance between two nuclei in a bond
• What is the trend of covalent radius across a period and down a group?

  • Across a period: Covalent radius decreases
  • Down a group: Covalent radius increases
• Why does the covalent radius decrease across a period?

  Due to increasing nuclear charge pulling the electron shell tighter
• Why does the covalent radius increase down a group?

  Because a new shell is added for each row, making the atom larger
• What is the definition of first ionization energy?

  It is the energy required to remove one mole of electrons from one mole of atoms in the gaseous state
• What is the trend of first ionization energy across a period?

  It generally increases due to increasing nuclear charge
• What is the trend of first ionization energy down a group?

  It generally decreases due to the shielding effect
• Why is the third ionization energy of magnesium significantly higher than the first and second?

  Because it involves removing an electron from a stable full outer shell
• What is electronegativity?


  Electronegativity is a measure of the attraction of an element for bonding electrons
• What is the trend of electronegativity across a period and down a group?

  • Across a period: Electronegativity increases
  • Down a group: Electronegativity decreases
• Why does electronegativity decrease down a group?

  Due to the screening or shielding effect from inner electron shells
• How are the chemical elements arranged in the periodic table?

  • In horizontal rows (periods) by increasing atomic number
  • In vertical columns (groups) based on similar reactivities
• What do elements in the same group of the periodic table have in common?

  They have similar reactivities due to a common number of outer electrons