Periodicity

  1. Why does CA increase going across the periodic table? Because the number of protons in the nucleus increases, leading to a stronger positive charge which exerts a greater attractive force on the electrons, pulling them closer to the nucleus and enhancing the Coulombic attraction

  2. Why does CA decrease going down the periodic table? Because as you move down a group, the electrons are added to increasingly higher energy levels, which means they are further away from the nucleus, resulting in a weaker attractive force between the positively charged nucleus and the negatively charged electrons

  3. Why does ionization energy increase as the atomic number increases in a period? Because the number of protons increases, leading to a stronger attraction between the nucleus and the outermost electrons, making it harder to remove an electron and requiring more energy to do so.

  4. Why does IE decrease going down a column? Because as you go down, the AR increases, meaning the valence electrons are further from the nucleus and experience less attraction, making them easier to remove and ionize. 

  5. Why does AR decrease going across a row? Because the number of protons increases, which results in a stronger positive charge that pulls the electrons closer to the nucleus, effectively shrinking the  atom’s size.

  6. Why does AR increase going down a column? Because the energy levels increase, meaning the valence electrons are further away from the nucleus, resulting in a larger atomic radius.

  7. Why does EN increase going across a row? Because the # protons increases, leading to a stronger positive charge that attracts electrons more strongly, making it harder for other atoms to pull them away

  8. Why does EN decrease going down a column? Because the AR increases, meaning the valence electrons are further away from the nucleus and experience more shielding from inner electrons, resulting in a weaker pull on shared electrons therefore lower electronegativity.

  9. Why does electron affinity increase going across a row?Because as the AR increases, the added electron is further away from the nucleus, experiencing a weaker attraction and therefore requiring less energy to be added. (The larger the atom, the less readily it wants to gain an electron.)

  10. Difference between atom and ion: An atom is neutral whereas an ion is charged. 

  11. Compare IR of metal atoms to that of metal ions: Metal atoms lose electrons to become ions; the valence shell is bigger.

  12. Compare IR of nonmetal atom to nonmetal ion: The number of electrons increases the repulsion of electrons to the valence shell, increasing the size of the ion.