Atomic Size Ionic Size Ionization Energy Electronegativity Periodic Table Trends Atomic Size Ionic Size Ionization Energy Electronegativity

Trends in Atomic Size Atomic Radius Trend: Half the diameter of an atom Measured in picometers (pm) Trend: Atomic size INCREASES down a group WHY? Energy levels are added down a group Atomic size DECREASES across a period WHY? Protons are added moving across a period, increasing the pull of attraction from the nucleus and pulling electrons closer.

Trends in Atomic Size

Practice: Which atom is larger? Explain why. Barium or Magnesium? ANSWER: Barium or Magnesium? Barium Farther down the group Sodium or Sulfur? Sodium Farther left in the period Oxygen or Chlorine? Chlorine Farther down the group Shielding effect more energy levels

Trends in Ionic Size (Ionic Radius) Cations are always SMALLER than the atoms from which they form. Why? Because they have lost electrons.

Trends in Ionic Size (Ionic Radius) Anions are always LARGER than the atoms from which they form. Why? Because they have gained electrons.

Trends in Ionic Size (Ionic Radius) Ionic size INCREASES down a group WHY? Energy levels are added down a group Ionic size DECREASES across a period WHY? Protons are added moving across a period, increasing the pull of attraction from the nucleus and pulling electrons closer. SAME TREND AS ATOMIC RADIUS!

Practice: Which ion is larger? Explain why. O or O2-? B or B3+? ANSWER: O or O2-? Oxide ion (O2-) Anion is larger than atom B or B3+? Boron atom (B) Cation is smaller than atom I1- or Br1-? Iodide ion (I1-) The iodide atom is farther down the group than the bromine atom

Trends in Ionization Energy Energy needed to REMOVE an electron from an atom. First Ionization Energy Energy required to remove the first electron Second Ionization Energy Energy required to remove the second electron Third Ionization Energy Energy required to remove the third electron

Trends in Ionization Energy Ionization Energy DECREASES down a group WHY? Electrons that occupy higher energy levels are easier to remove because they are farther from the nucleus. Ionization Energy INCREASES across a period WHY? As protons are added across a period, the electrons are harder to remove because the nucleus is pulling them with a greater force. OPPOSITE trend from Atomic & Ionic Radii!

IONIZATION ENERGY TREND Helium has the highest ionization energy Francium has the lowest ionization energy

Practice: Which has a greater first ionization energy? ANSWER: Potassium or Sulfur? Sulfur Farther to the right Lithium or Francium? Lithium Farther to the top Carbon or Phosphorus? Carbon Farther to the top Fewer energy levels, stronger force of attraction

Trends in Electronegativity Ability of an atom to attract electrons when the atom is in a compound. When looking at this trend, we IGNORE the noble gases because they to not have the ability to attract electrons when in a compound since they have a filled s & p sublevels.

Trends in Electronegativity Electronegativity DECREASES down a group WHY? Electrons that occupy higher energy levels are easier to remove because they are farther from the nucleus. Electronegativity INCREASES across a period WHY? As protons are added across a period, the electrons are harder to remove because the nucleus is pulling them with a greater force. SAME TREND AS IONIZATION ENERGY!

ELECTRONEGATIVITY TREND Fluorine is the most electronegative element Francium is the least electronegative element

Practice: Which has a greater electronegativity? Chlorine or Iodine? ANSWER: Chlorine or Iodine? Chlorine Farther to the top Phosphorus or Magnesium? Phosphorus Farther to the right Strontium or Potassium? Strontium Farther to the right Stronger force of attraction